GENERA OF PTERIDOSPERMS, FERNS, AND _PLANTAE
INCERTAE SEDIS._
The genera and species described in this Chapter are founded on
sterile leaves or portions of leaves, and in the great majority of
cases the reproductive organs are either imperfectly known or have
still to be discovered. Some of the genera, the smaller number, are
no doubt true ferns, while most of them may safely be regarded as
plants which will ultimately be shown to belong to some other group,
in most cases that of the Pteridosperms. It is possible that a few
of the types may be members of the Cycadophyta rather than of the
Pteridospermeae, but evidence as to systematic position is for the
most part of a negative kind or too incomplete to lead to any definite
expression of opinion as to the cycadean or pteridosperm nature of the
imperfectly known Palaeozoic or Mesozoic species. Many of the genera
are of little botanical interest, though even the most problematical
are of importance as criteria of geological age. Genera which there
is good reason for including in the Pteridosperms are dealt with in
this section, in order that the Chapter in Volume III. devoted to this
important group may be limited to more completely known types.
In most text-books it is customary to employ family names for sterile
fern-like fronds which possess similar venation features or have
in common certain vegetative characters, the value of which it is
impossible to estimate. In the following account family or group
names are not adopted, on the ground that such slight utility as
they may have is more than counterbalanced by the risk attending a
grouping under one name of plants which may agree only in unessential
characters. The practice of classifying fossil plants has been carried
to excess. Grouping together genera as a matter of convenience
unavoidably creates a prejudice in favour of actual relationship, which
may or may not exist.
Taeniopteris.
This generic name was instituted by Brongniart[1254] for simple
linear or broadly linear leaves with a prominent midrib from which
secondary veins, simple or dichotomously branched, are given off at
right angles or obliquely. The frond of the type-species _Taeniopteris
vittata_ (fig. 332), characteristic of Jurassic floras, was compared
by Brongniart with the pinnules of _Danaea_ and _Angiopteris_. Among
recent ferns the Taeniopteris form of frond and venation is represented
by _Oleandra neriiformis_, _Asplenium nidus_, and many other species.
Though usually applied to fronds which there is good reason for
regarding as simple leaves, the generic designation _Taeniopteris_ has
been extended to include pinnate fronds, e.g. the Upper Palaeozoic
species _T. jejunata_ Grand’Eury, and _T. Carnoti_ Ren. and Zeill.
(fig. 330, A). The compound fronds from the Lower Coal-Measures
of Missouri described by Dr White[1255] as _T. missouriensis_ are
characterised by decurrent and confluent Taeniopteroid pinnules. In a
later reference[1256] to this plant White pertinently adds, “perhaps it
belongs more properly in _Alethopteris_.”
Leaves of the _Taeniopteris_ type are described by several authors as
species of _Oleandridium_, _Angiopteridium_, _Danaeites_, _Marattia_,
and other genera. In such species of Taeniopteroid leaves as have
been dealt with in a former Chapter, the occurrence of sori justifies
the substitution of a name denoting a close relationship to existing
members of the Marattiaceae, but in the absence of fertile specimens
the provisional designation _Taeniopteris_ should be retained. It
is often difficult to decide between _Taeniopteris_ and _Nilssonia_
as the more suitable name to apply to fragments of fossil leaves
of Mesozoic age. _Taeniopteris_ is, however, distinguished from the
Cycadean genus by the greater prominence of the rachis, also by the
dichotomous branching of the secondary veins, usually close to their
origin and at varying distances between the axis of the frond and the
edge of the lamina. The genus _Taeniopteris_, though most abundant in
Rhaetic and Jurassic strata, occurs also in Upper Carboniferous and
Lower Permian rocks. The generic name _Macrotaeniopteris_ instituted by
Schimper[1257] has been used for leaves differing only in size from the
usual type of _Taeniopteris_, but there is no adequate reason for its
retention.
The species included in _Taeniopteris_ afford no satisfactory evidence
as to their systematic position. It is obviously unwise to adopt such
generic titles as _Oleandridium_, _Marattiopsis_, etc., merely because
of resemblance in the venation of sterile fragments to _Oleandra_ or
Marattiaceous ferns.
Some specimens of _Taeniopteris_ fronds described by Mr Sellards[1258]
from Permian rocks of Kansas, which are referred to later, have
furnished unconvincing evidence of reproductive organs.
_Taeniopteris multinervis_, Weiss. Fig. 329, A, B.
The late Dr Weiss[1259] instituted this species (which he designated
_Taeniopteris multinervia_, though the specific name _multinervis_
is constantly used) for a fragment of a leaf from the Lower Permian
of Lebach characterised by numerous forked veins given off at right
angles from a prominent rachis (fig. 329, B). This type of frond is
recorded from the Permian of Trienbach (Alsace) by Zeiller[1260], by
Renault[1261] and Zeiller[1262] from the Upper Carboniferous of Autun,
and from other localities. The lamina of the simple leaf reaches a
breadth of 6 cm. and a length of 40 cm. (fig. 329, A); the numerous
secondary veins (25–36 per cm. of lamina) are either at right angles
to the rachis or given off at an acute angle. The mesophyll consists
of polygonal cells some of which are elongated at right angles to the
surface of the lamina. A very similar form is described by Fontaine and
White from the Permian of Virginia as _T. Lescuriana_[1263].
[Illustration: FIG. 329.
A. _Taeniopteris multinervis_, Weiss. (⅚ nat. size. After Zeiller.)
B. _T. multinervis._ (Enlarged. After Zeiller.)
C. _Lesleya Delafondi._ (× 2. After Zeiller.)]
It is futile to expect to be able to separate the numerous
_Taeniopteris_ leaves into well-defined species: all we can do is
to group the specimens under different names, using as artificial
distinctions such characters as the shape of the leaf, the number
of veins per centimetre, and the prominence of the rachis.
Another Virginian species of Permian age described by Fontaine
and White[1264], _T. Newberriana_, is said to bear sori, but no
satisfactory information is given as to the nature of these organs.
Specimens referred with some hesitation to this species and to a
similar species, _T. coriacea_, have been described by Sellards[1265]
from material obtained from Permian beds in Kansas. The lamina of the
simple linear fronds is characterised by the occurrence of small oval
bodies half immersed in the substance of the leaf between the secondary
veins (figs. 330, D, E). One of these bodies is represented in an
apparently dehisced condition in fig. 330, D. Sellards suggests the
possibility that these bodies are sporangia, but, as he points out,
they afford no indication of cellular structure nor are they in direct
connexion with the veins.
_Taeniopteris jejunata_, Grand’Eury[1266].
This species differs from _T. multinervis_ in its bipinnate fronds;
the linear or oval-linear pinnae are attached by a short stalk to
the primary rachis and reach a length of 25 cm.; the veins are less
crowded, 12–15 per centimetre.
_T. jejunata_ is recorded from the Coal-fields of the Loire and
Commentry[1267] in France, from the Lower Permian of Thuringia[1268],
and elsewhere.
_Taeniopteris Carnoti_, Ren. and Zeiller[1269]. Fig. 330, A.
This species, founded on portions of pinnate fronds from the Coal-field
of Commentry, is characterised by rather broader (25–30 mm.) pinnules,
with short pedicels and a cordate base, reaching a length of 25–30 cm.
The secondary forked veins are more numerous than in _T. jejunata_. In
_T. multinervis_ the pinnules are still broader and have a stronger
midrib.
• • • • •
Several species of _Taeniopteris_ have been described from
Triasso-Rhaetic rocks in Europe, India, Tonkin and elsewhere. In
some cases it is practically impossible to recognise clear specific
distinctions between Rhaetic and Jurassic types.
From the Damuda and Panchet series of India (Triasso-Rhaetic)
Feistmantel has described large sterile fronds as _Macrotaeniopteris
Feddeni_[1270] which reach a breadth of 20 cm.: these may be compared
with the Indian species _Taeniopteris lata_ Oldham[1271], and to _T.
gigantea_ from the Rhaetic of Franconia[1272] and Scania. A specimen
of this species figured by Nathorst[1273] from Scania has a lamina 33
cm. broad. Other examples are afforded by _M. Wianamattae_ Feist.[1274]
from rocks of the same age in Australia and by _Taeniopteris superba_
Sap.[1275] from Lower Rhaetic rocks near Autun.
From the Rhaetic of Tonkin, Zeiller records several species, among
which may be mentioned _T. Jourdyi_ Zeill.[1276] and _T. spatulata_
MacClelland (fig. 330, B, C). Both have simple fronds. Those of _T.
Jourdyi_ reach a length of 10–40 cm. and a breadth of 10–70 mm.; the
rachis is characterised by crowded and discontinuous transverse folds,
and the secondary veins (35–50 per cm.) are usually at right angles
to the rachis. This Tonkin species is compared by Zeiller with the
European Rhaetic species _T. tenuinervis_ Brauns.
The polymorphism of the fronds is a striking feature: in one
case described by Zeiller the lamina appears to be divided into
segments like those characteristic of the leaf of the Cycadean
genus _Anomozamites_. It is obviously difficult in many instances
to distinguish between detached Taeniopteroid pinnae of a compound
frond and complete simple leaves. In some compound fern fronds, as
in the recent Polypodiaceous genus _Didymochlaena_, the pinnules are
deciduous, and the same feature undoubtedly characterised the fronds of
many extinct species. A specimen figured by Zeiller which shows several
petioles of _T. Jourdyi_ attached to a thick stem[1277] demonstrates
the simple nature of the leaves. In other cases, e.g. _T. vittata_,
specimens occur in which the slightly enlarged petiole-base has a
clean-cut surface indicating abscission from a rhizome (fig. 332).
The fronds described by Zeiller as _T. spatulata_[1278] (fig. 330,
B, C) closely resemble Jurassic leaves from Victoria referred to
_Taeniopteris Daintreei_ McCoy[1279].
[Illustration: FIG. 330.
A. _Taeniopteris Carnoti_, Ren. and Zeill. (Nat. size. After
Renault and Zeiller.)
B. _T. spatulata_, McClell. (Nat. size. After Zeiller.)
C. _T. spatulata._ (× 3. After Zeiller.)
D. Supposed sporangium of _T. coriacea._ (× 15. After Sellards.)
E. _T. coriacea._ (× 2. After Sellards.)]
Whether specifically identical or not, these leaves represent a
type distinguished from the other species of the genus by the small
breadth of the linear-lanceolate or linear-spathulate lamina, which
may be 6–15 cm. in length and 3–12 mm. broad. The lamina is often
characterised by transverse folds (fig. 330, C).
_Taeniopteris Carruthersi._ Fig. 331.
1872. _Taeniopteris Daintreei_, Carruthers, Quart. Journ. Geol. Soc.
Vol. XXVIII. Pl. XXVII. fig. 6.
1883. _T. Carruthersi_, Tenison-Woods, Proc. Linn. Soc. N. S. Wales,
Vol. VIII. p. 117.
[Illustration: FIG. 331. _Taeniopteris Carruthersi_, Ten.-Woods. Nat.
size.]
The simple fronds included under this specific name are characterised
by a strong midrib from which numerous simple or forked secondary veins
are given off at a right angle or slightly inclined. The breadth of the
lamina decreases gradually towards the petiole. The Australian species
named by McCoy _Taeniopteris Daintreei_, to which Carruthers referred
the Queensland fossils, has a much narrower and more linear form of
frond, and for this reason Tenison-Woods instituted a new specific
name. _T. Carruthersi_ represents a form of leaf met with in Rhaetic,
or possibly Upper Triassic, rocks in S. Africa[1280] and Australia. A
very similar, perhaps an identical type, was described from Argentina
by Geinitz[1281] as _T. mareyiaca_: among many other examples of
this form of frond may be mentioned _T. immersa_[1282] Nath. from
the Rhaetic rocks of Scania and _T. virgulata_ from the Rhaetic of
Tonkin[1283].
A comparison of _Taeniopteris Carruthersi_ or various other “species”
of Rhaetic fronds with the Jurassic species _T. vittata_ illustrates
the slight and unimportant differences on which specific separation is
based. It is hopeless to attempt to draw a satisfactory distinction
between the numerous Taeniopteris fronds from Upper Triassic and
Jurassic rocks.
_Taeniopteris vittata_, Brongniart. Fig. 332.
The simple leaves to which Brongniart applied this name are
characteristic of the Inferior Oolite flora of England, and examples of
the same type are recorded from Jurassic rocks of India, Poland, the
Arctic regions, Japan, China, Australia and other countries[1284].
Leaf linear-lanceolate, reaching a length of more than 20 cm. and
a breadth of 3 cm. The lamina increases gradually in breadth from
the base and tapers towards the apex. Numerous secondary veins are
given off at right angles from a broad midrib: the lateral veins
may be simple or forked close to their origin, near the margin, or
in the intermediate portion, of the lamina.
It is exceedingly difficult to use _Taeniopteris_ leaves of this
form as evidence in regard to the Jurassic or Rhaetic age of
plant-bearing strata. The species _T. tenuinervis_ Brauns, as figured
by Schenk[1285] from the Rhaetic rocks of Germany and Persia, and
recorded from several other regions, presents a close agreement with
_T. vittata_. _Oleandridium lentriculiforme_ Etheridge[1286] from the
Hawkesbury series of Australia is another similar leaf. The species _T.
vittata_ from the Yorkshire coast, represented in fig. 332, shows a
well-preserved petiole with a clean-cut base like that of the petioles
of _Oleandra neriiformis_ and other recent ferns which are detached
from the rhizome by the action of an absciss-layer.
[Illustration: FIG. 332. _Taeniopteris vittata._ (British Museum No.
39217. ⅔ nat. size.)]
A broader form of frond with similar venation was described by
Lindley and Hutton[1287] as _Taeniopteris major_. An examination of
the type-specimen from the Inferior Oolite of Yorkshire, now in the
Manchester Museum, led me to doubt the necessity of specific separation
from _T. vittata_[1288].
A smaller frond of the same general type as _T. vittata_ is recorded
from Wealden strata of North Germany and England under the name _T.
Beyrichii_[1289].
Weichselia.
This generic name was instituted by Stiehler[1290] for impressions
of bipinnate sterile fronds, presumably ferns, from Lower Cretaceous
rocks near Quedlinburg. The same type of leaf from English Wealden
beds had previously been referred by Mantell and other authors to
_Pecopteris_, and by Brongniart to his genus _Lonchopteris_[1291].
It is, however, advisable to follow Nathorst’s example[1292] and
restrict the latter name to Palaeozoic species. As already suggested,
it would obviate confusion to substitute a new generic designation
for _Lonchopteris_ in the case of Triassic species which are probably
members of the Osmundaceae. The type-species of Stiehler, _Weichselia
Ludowicae_[1293], does not differ in any important character from
_Weichselia Mantelli_, the species originally described by Stokes and
Webb from the Wealden of England as _Pecopteris reticulata_.
_Weichselia Mantelli_ (Brongn.)[1294]. Fig. 333.
1824. _Pecopteris reticulata_, Stokes and Webb, Trans. Geol. Soc.
[2]. Vol. I. p. 423, Pls. XLVI. XLVII.
1828. _Lonchopteris Mantelli_, Brongniart, Prod. p. 6; Hist. vég.
foss. p. 369, Pl. CXXXI.
1894. _Weichselia Mantelli_, Seward, Wealden Flora, Vol. I. p. 114.
Pl. X. fig. 3.
1899. _Weichselia reticulata_, Fontaine, in Ward, Ann. Rep. U. S.
Geol. Surv. p. 651.
Frond bipinnate, rachis broad; pinnae very long, of uniform breadth
and with prominent axes; pinnules crowded, entire, with obtuse
apex, usually oblong but more or less triangular or rounded towards
the distal ends of the pinnae. The pinnules, which may reach a
length of 9 cm., are characterised by a fleshy lamina attached by
the whole breadth of the base; the two rows of segments on each
secondary rachis are usually inclined towards one another so that
they form with the axis of the pinna a wide-open =V= instead of
lying in one plane (fig. 333, C). From a median rib are given off
numerous anastomosing branches (fig. 333, B).
[Illustration: FIG. 333. _Weichselia Mantelli._
A. Part of a frond from the Wealden of Sussex, England. (British
Museum; v. 2630. ¾ nat. size.)
B. Pinnule from Bernissart, Belgium (× 3).
C. _Weichselia erratica_, Nath. Section of pinna. (After Nathorst.)]
This characteristic Wealden species is recorded from England, Germany,
France, Belgium, Austria, Russia, Bornholm, North America, and Japan.
It is by no means certain that _Weichselia Mantelli_ is a true fern: no
satisfactory evidence of fructification has been adduced.
The broad and strong rachis is comparable with that of a Cycadean leaf
and the thick lamina suggests a plant of xerophilous habit. I have
retained the specific name _Mantelli_ on the ground of long established
usage instead of following Fontaine in his adherence to strict priority.
Glossopteris.
The name _Glossopteris_ was proposed by Brongniart in 1822[1295] for an
imperfect leaf-impression which he called _Filicites_ (_Glossopteris_)
_dubius_, but the specimen so named has since been identified as
part of a sporophyll of a _Lepidostrobus_. The author of the genus
afterwards published[1296] a diagnosis, based on well-preserved
leaves from Permo-Carboniferous rocks in Australia and India, of the
type-species _Glossopteris Browniana_, the Indian examples being
distinguished as _G. Browniana_ var. _indica_ while the Australian
form was named _G. Browniana_ var. _australasica_. Schimper[1297]
afterwards raised the Indian fossils to specific rank as _G. indica_
though some authors[1298] have continued to consider the two forms as
insufficiently distinct to be regarded as different species.
The genus _Glossopteris_ may be defined as follows:
Leaves simple, varying considerably in size, shape, and venation
characters, but almost without exception characterised by
repeatedly anastomosing lateral veins. The leaves are of two
kinds: (i) _foliage leaves_; apparently always sterile, usually
spathulate, with an obtuse apex, a well-marked midrib which may
persist to the apex or die out in the upper half of the lamina,
characterised by its slight prominence and comparatively great
breadth especially in the basal part of the frond. In most cases
the lamina extends as a narrow margin to the leaf-base, but in
a few forms there is a short petiole (fig. 334). Though usually
spathulate, the frond may be linear-lanceolate, or ovate; the
apex is sometimes acute. Leaves vary in length from 3 to 40 cm.
and may in larger forms have a breadth of 10 cm. Numerous lateral
veins curve upwards and outwards to the margin of the lamina or
pursue a straight course almost at right-angles to the midrib. (ii)
_Scale-leaves_[1299] which differ from the foliage-leaves in their
much smaller size and in the absence of a midrib; they are deltoid,
oval or cordate in shape and generally terminate in an acute apex;
the edge of the lamina may be slightly incurved so that the leaf
presents a convex upper surface supplied with anastomosing veins.
The scale-leaves, which vary in length from about 1 to 6 cm.,
probably acted as sporophylls. The only evidence as to the nature
of the fructification so far obtained is represented by empty
sporangium-like organs (1·2–1·5 mm. long by 0·6–0·8 mm. broad)
frequently associated with the scale-leaves[1300].
The leaves, in some cases at least, were borne near together on a
cylindrical stem or rhizome which produced branched adventitious
roots[1301]. The fossils long known as _Vertebraria_ were
recognised by Zeiller[1302] and by Oldham[1303] as the stems of
_Glossopteris_.
The systematic position of _Glossopteris_ must for the present be left
an open question. Though usually spoken of as a fern, it is noteworthy
that despite the enormous abundance of its foliage leaves in the
Permo-Carboniferous strata of India, Australia, South Africa, and South
America, no single example has been discovered which shows undoubted
remains of sori or sporangia. Many authors have described fertile
leaves of _Glossopteris_; but it was not until Arber’s discovery of
sporangia in close association with the scale-leaves that any light was
thrown on the nature of the reproductive organs.
The probability is that _Glossopteris_ was not a true fern but a
member of that large and ever-increasing class, the Pteridosperms.
This opinion is based largely on negative evidence. Such sporangia as
have been described may have contained microspores and the plant may
have been heterosporous. The occurrence of seeds in association with
Glossopteris fronds recorded by more than one writer[1304], though
by no means decisive and possibly the result of chance association,
is favourable to this view. Dr White[1305] has suggested that the
small leaves described by Zeiller[1306] as _Ottokaria bengalensis_
from Lower Gondwana (Permo-Carboniferous) rocks of India, and similar
fossils recorded by himself from Brazil as _O. ovalis_, may represent
“sporangiferous” organs of _Glossopteris_ or _Gangamopteris_, “both of
which are probably pteridospermic.” There is, however, no conclusive
evidence in support of this suggestion.
The genus, whatever its position may be, has a special interest for
the geologist and for the student of plant distribution; it is a
characteristic member of a Permo-Carboniferous flora which flourished
over an enormous area, including India, South Africa,—extending from
Cape Colony to Rhodesia and German East Africa[1307],—Australia,
and South America[1308]. This flora, known as the Glossopteris
flora, differed considerably in its component genera from that which
overspread Europe and North America and some more southern regions in
the Upper Carboniferous and Permian periods.
The discovery by Amalitzky[1309] of _Glossopteris_, and other genera
characteristic of the Glossopteris flora, in the Upper Permian rocks
in Vologda (Russia) demonstrates the existence of a northern outpost
of the southern botanical province, and Zeiller’s discovery of the
genus in the Rhaetic flora of Tonkin[1310] shows that _Glossopteris_
persisted beyond the limits of the Palaeozoic epoch. Dr David
White[1311] has recently proposed to re-christen the Glossopteris flora
the Gangamopteris flora on the ground that _Gangamopteris_ is strictly
Palaeozoic in its range, whereas _Glossopteris_ persisted into the
Mesozoic era; this is perhaps hardly a sufficient reason for giving up
so well established a title as the Glossopteris flora. A fuller account
of this southern flora must be reserved for another volume.
_Glossopteris Browniana_, Brongniart[1312]. Figs. 334–36.
The specific name _Browniana_ is now applied to obtusely pointed
leaves which sometimes reach a length of 15 cm., but are usually
rather shorter. In form and venation they closely resemble the leaves
of the recent genus _Antrophyum_ and species of _Acrostichum_. The
comparatively broad midrib may be replaced in its proximal portion by
several parallel veins: from it are given off numerous lateral veins
which form a reticulum characterised by meshes approximately equal in
size and elongated in a direction parallel to the general course of the
secondary veins (fig. 334).
[Illustration: FIG. 334. _Glossopteris Browniana_, Brongn. A. Nat.
size: B × 3½.]
The drawings, originally published by Zeiller[1313], reproduced in fig.
335 illustrate the venation and its range of variation; the meshes
are usually hexagonal and arranged as shown in figs. A and B, but
occasionally (fig. 335, C) they follow a more steeply inclined course.
Small leaves with a more or less distinct midrib, 2–3 cm. in length,
supply transitional stages between foliage- and scale-leaves. In the
true scale-leaves spreading and occasionally anastomosing veins take
the place of the midrib and lateral veins of the ordinary frond.
McCoy[1314] in describing some Australian specimens of _Glossopteris_
in 1847 spoke of scale-like appendages of the rhizome which he
compared with the large ramenta of _Acrostichum_ and other ferns. It
was, however, Zeiller[1315] who first recognised the leaf-nature of
these scales and adequately described them; additional figures of
scale-leaves have been published by Mr Arber[1316] and by myself[1317].
The importance of these small leaves has been considerably increased
by Mr Arber’s discovery of associated sporangia which, as he suggests,
were probably borne on their lower concave surface.
[Illustration: FIG. 335. _Glossopteris Browniana_, Brongn. (After
Zeiller. × 2.)]
The sporangia (fig. 336) are compared by Arber with the microsporangia
of recent Cycads and with the Palaeozoic sporangia described by Zeiller
as _Discopteris Rallii_ (fig. 256, D); the latter are distinguished by
the well-defined group of thicker walled cells representing the annulus
of true fern sporangia. We know nothing as to the contents of the
Glossopteris sporangia, whether they contained microspores or whether
they are the spore-capsules of a homosporous plant.
[Illustration: FIG. 336. _Glossopteris Browniana_, Brongn. Sporangia.
(× 30). After Arber.]
The rhizome of _Glossopteris Browniana_ has been described in detail by
Zeiller, who first demonstrated that the fossils originally assigned by
Royle[1318] to the genus _Vertebraria_ represent the stem of this and,
as we now know, of some other species of _Glossopteris_. _Vertebraria_
occurs in abundance in Permo-Carboniferous strata in association with
_Glossopteris_; the differences between Australian, Indian, and South
forms, though expressed by specific names, are insignificant. The stems
are usually preserved in the form of flattened, single or branched,
axes sometimes bearing slender branched roots and characterised by
one or two, or less frequently three, longitudinal grooves or ridges
(fig. 337) from which lateral grooves or ridges are given off at right
angles, dividing the surface into more or less rectangular areas 1
cm. or more in length. The surface of these areas is often slightly
convex and in some specimens the outlines of cells may be detected. Mr
Oldham has described some interesting examples of _Vertebraria_ from
India in which the longitudinal and transverse grooves are occupied
by a dark brown ferruginous substance or by the carbonised remains of
plant-tissues (fig. 338, C, D). In transverse section, a _Vertebraria_
cast appears to be divided into a number of wedge-shaped segments
radiating from a common centre. Prof. Zeiller[1319] has figured
specimens of _Vertebraria_ with portions of Glossopteris fronds still
attached.
[Illustration: FIG. 337. _Vertebraria indica_, Royle. Nat. size. (After
Feistmantel.)]
The rhizome of _Glossopteris_, as represented by the Vertebraria
casts, is aptly compared by Zeiller[1320] with that of the recent
Polypodiaceous fern _Onoclea struthiopteris_. Sections of the recent
stem (fig. 338, E, F) show that the form is irregularly stellate
owing to the presence of prominent wings which anastomose laterally
at intervals as shown by the examination of a series of sections. The
leaf-traces are derived from the steles of adjacent wings. Fig. 338
(B and A) represents somewhat diagrammatically a longitudinal and
transverse view of a _Vertebraria_; the radiating arms represented in
the transverse section (fig. A) are the stem ribs or wings and the
segments between them are intrusions of sedimentary material. The
rectangular areas characteristic of the surface of a _Vertebraria_ are
the intruded segments of rock: these are separated at intervals by
transverse grooves, which mark the course of vascular strands given off
at each anastomosis of the longitudinal wings to supply the leaves.
[Illustration: FIG. 338.
A, B. _Vertebraria indica._ (After Zeiller.)
C, D. _V. indica._ (Nat. size. After Oldham.)
E, F. _Onoclea struthiopteris._ (× 2. After Zeiller.)]
Mr Oldham, who discovered the connexion between _Glossopteris_ and
_Vertebraria_ independently of Dr Zeiller, does not agree with the
interpretation of the structural features of the rhizome which Zeiller
bases on a comparison between Vertebraria and _Onoclea struthiopteris_.
Oldham[1321] describes _Vertebraria_ as consisting of a central axis
“joined to an outer rind by a series of radial septa,” the spaces
between the septa being divided into chambers by transverse partitions.
His view is that the rhizome of _Glossopteris_ was a cylindrical
organ and not an irregularly winged axis like the stem of _Onoclea_.
Zeiller[1322] has replied in detail to Oldham’s interpretation and
adheres to his original view, that the rhizome consisted of a solid
axis with radial wings or flanges which at intervals anastomosed
transversely in pairs at the nodes. It may, however, be possible
that the spaces between the longitudinal and transverse grooves on a
Vertebraria axis, which have been filled with the surrounding rock,
were originally occupied in part at least by secondary wood, and the
transverse strips of carbonaceous material[1323] lying in the grooves
may represent medullary-ray tissue and accompanying leaf-traces. The
longitudinal striations seen in some specimens of _Vertebraria_ on the
areas between the grooves may be the impressions of woody tissue. It
is impossible without the aid of more perfectly preserved material to
arrive at a satisfactory conception of the structural features of a
complete Glossopteris rhizome.
[Illustration: FIG. 339. _Glossopteris_ fronds attached to rhizome.
(From a specimen lent by Dr Mohlengraaff. Considerably reduced.)]
In the specimen of _Glossopteris Browniana_ shown in fig. 339
several leaves are attached to an axis which shows none of the
surface-features of _Vertebraria_. I am indebted to the kindness of
Dr Mohlengraaff of Delft for the loan of this specimen which was
obtained from Permo-Carboniferous rocks in the Transvaal. An axis
figured by Etheridge[1324] from an Australian locality bears a tuft
of _Glossopteris_ leaves, possibly _G. Browniana_; in place of the
rectangular areas characteristic of _Vertebraria_ it shows transversely
elongated leaf-scars or, on the internal cast, imbricate rod-like
projections which Etheridge suggests represent vascular bundles.
_Glossopteris indica_, Schimper. Figs. 340, A, 341.
It is a question of secondary importance whether or not the fronds
which Brongniart spoke of as a variety of _Glossopteris Browniana_
should be recognised as specifically distinct. The careful examination
by Zeiller of the venation characters has, however, afforded
justification for separating _G. Browniana_ and _G. indica_. We must
admit that the slight and not very constant differences in the size
and form of the meshes produced by the anastomosing of the lateral
veins are characters which cannot be recognised as having more than
a secondary value, though, as a matter of convenience, we employ
them as aids to determination. The arbitrary separation of sterile
leaves, which differ by small degrees from one another in form and in
the details of venation, by the application of specific names is a
thankless task necessitated by custom and convenience; it is, however,
idle to ignore the artificial basis of such separation. Mr Arber has
recently published, in his valuable _Glossopteris Flora_, an analytical
key which serves to facilitate the description and determination of
different types of frond[1325].
[Illustration: FIG. 340.
A. _Glossopteris indica_, Schimper. (½ nat. size.)
B. _Glossopteris angustifolia_, Brongniart. (Nat. size.) From Arber,
after Feistmantel.]
The large leaves of _Glossopteris indica_, reaching a length in
extreme cases of 40 cm. and a breadth of 10 cm., are characterised
by a rather greater regularity in the arrangement of the meshes and
by the greater parallelism of the upper and lower sides of each mesh
(fig. 341) and by less difference in size between the venation meshes
than in _G. Browniana_, the leaves of which are usually smaller. The
relatively thick epidermis consists of rectangular cells with stomata
in depressions[1326]. The scale-leaves[1327], rather larger than those
of _G. Browniana_, are more or less rhomboidal with rounded angles and
reach a length of 1·5–6 cm. and a breadth of 1·5–2·5 cm. The rhizome is
practically identical with that of _G. Browniana_[1328].
[Illustration: FIG. 341. _Glossopteris indica_, Schimp. (× 1½.) From
Arber, after Zeiller.]
This species occurs in great abundance in the Permo-Carboniferous
rocks of India, Australia, and in various parts of South Africa,
and elsewhere. It has been recognised also by Amalitzky[1329] in
Upper Permian beds in Russia and by Zeiller in the Rhaetic series of
Tonkin[1330].
[Illustration: FIG. 342. _Glossopteris angustifolia_ var.
_taeniopteroides_. (× 3½.)]
_Glossopteris angustifolia_, Brongniart. Figs. 340, B; 342.
It is convenient to retain this designation for linear fronds with an
acute or obtuse apex and a venation-reticulum composed of long and
narrow meshes (fig. 340, B). It is by no means unlikely, as Arber
suggests, that the same plant may have produced leaves of the _G.
indica_ type and narrower fronds which conform to _G. angustifolia_.
In his description of some Indian specimens of _G. indica_, Zeiller
draws attention to the variation exhibited in regard to the extent
of anastomosing between the secondary veins: some examples with very
few cross-connexions agree more closely with _Taeniopteris_ than
with _Glossopteris_ as usually defined[1331]. The venation shown in
fig. 342 illustrates an extreme case of what is almost certainly a
Glossopteris leaf of the _G. angustifolia_ type. This specimen, which
was discovered by Mr Leslie in the Permo-Carboniferous sandstone of
Vereeniging (Transvaal), has been referred to a variety of Brongniart’s
species as _G. angustifolia_ var. _taeniopteroides_[1332] on account
of the almost complete absence of any cross-connexions. The reference
to _Glossopteris_, which my friend Dr Zeiller suggested, is amply
justified by the form of the leaf as a whole, by the angle at which
the lateral veins leave the midrib, a feature in contrast to the
wider angle at which the lateral veins are usually given off in
_Taeniopteris_ (figs. 329, 332), and by the similarity to the Indian
specimens already mentioned. Several authors have described leaves or
leaflets under the generic name _Megalopteris_[1333] from Carboniferous
and Permian rocks which bear a close resemblance to the South African
variety, but in some cases at least _Megalopteris_ is known to be a
pinnate and not a simple leaf. The leaf figured by Jack and Etheridge
as _Taeniopteris_ sp.[1334] from Queensland may also be an example of
_Glossopteris_. Comparison may be made also with the Palaeozoic leaves
described in the first instance by Lesquereux and more recently by
Renault and Zeiller as species of _Lesleya_[1335] (fig. 347).
[Illustration: FIG. 343. _Blechnoxylon talbragarense_, Eth.: _s_,
scale-leaves; _x_, secondary xylem. (After Etheridge. A × 2; B × 3;
C much enlarged.)]
_Blechnoxylon talbragarense_, Etheridge. Fig. 343.
Under this name Etheridge[1336] described some specimens from the
Permo-Carboniferous Coal-Measures of New South Wales, which he regards
as a fern, comparable, in the possession of a cylinder of secondary
xylem, with the recent genus _Botrychium_ and with _Lyginodendron_
and other members of the Cycadofilices. The slender axis (1–3 mm. in
diameter) appears to consist of a zone of radially disposed tissue
(fig. 343, C, _x_), which is probably of the nature of secondary
xylem, enclosing a pith and surrounded externally by imperfectly
preserved remnants of cortex. Unfortunately no anatomical details
could be made out, but the general appearance, if not due to inorganic
structure, certainly supports Etheridge’s determination. The stem
bore at intervals clusters of linear-lanceolate leaves (reaching 12
mm. in length) in close spirals (fig. 343, A and B); the leaves are
characterised by a strong midrib and forked secondary veins. Small
“pyriform” bodies of the nature of scale-leaves occur in association
with the fronds (fig. 343, B, _s_).
In his description of this interesting plant, Etheridge quotes an
opinion which I expressed in regard to the comparison of the stem
with those of _Botrychium_, _Lyginodendron_, and other genera.
No satisfactory evidence has been found as to the nature of the
fructification. Although the leaves of _Blechnoxylon_ are much smaller
than those of _Glossopteris_, I am now disposed to regard the genus
as closely allied or even generically referable to _Glossopteris_.
The crowded disposition of the leaves is like that in _Glossopteris_,
shown in fig. 339 and in the figures published by Etheridge and by
Oldham; the association of scale-leaves and foliage-leaves is another
feature in common. The absence of a reticulum of anastomosing veins
can no longer be considered a fatal objection to the suggestion that
the Australian type may be a species of _Glossopteris_. If the view
that _Blechnoxylon_ is not a distinct genus is correct, the occurrence
of secondary xylem is favourable to the opinion already expressed
that _Glossopteris_ is more likely to be a Pteridosperm than a true
fern. The data at present available render it advisable to retain Mr
Etheridge’s name: the comparison with _Glossopteris_ lacks confirmation.
[Sidenote: BLECHNOXYLON]
[Illustration: FIG. 344. _Glossopteris retifera._ (Nat. size. From
Arber, after Feistmantel.)]
_Glossopteris retifera_, Feist. Fig. 344.
In some _Glossopteris_ leaves the anastomosing secondary veins form
a coarser reticulum, as in the example represented in fig. 344. The
name _G. retifera_ was given by Feistmantel[1337] to Indian fronds of
this type; similar forms have been described as _G. conspicua_ and _G.
Tatei_. The type illustrated by _G. retifera_ is recorded also from
Permo-Carboniferous rocks in Zululand[1338], Natal, the Transvaal, Cape
Colony, and the Argentine.
Gangamopteris.
In 1847 McCoy[1339] described a leaf-fragment from Permo-Carboniferous
rocks in New South Wales as _Cyclopteris angustifolia_. The
type-specimen of this species, which is now in the Sedgwick Museum,
Cambridge, has been re-described by Mr Arber[1340]. Subsequently[1341]
McCoy instituted the generic name _Gangamopteris_ for leaves, like
that previously referred by him to _Cyclopteris_, from the Bacchus
Marsh Sandstone, of New South Wales, but he did not publish a diagnosis
of the genus until several years later[1342]. Feistmantel[1343], who
has described many species of _Gangamopteris_ from the Lower Gondwana
strata of India, slightly modified the original diagnosis. The genus
is represented by sterile fronds only. We know nothing of the stem,
and such evidence as is available in regard to the form of the fertile
leaves is of a circumstantial kind. It is, however, highly probable
that _Gangamopteris_ is not a true fern but a Pteridosperm.
Leaves simple, sessile, varying in shape; obovate or spathulate,
broadly lanceolate or rarely linear; the apex is usually blunt
(fig. 345) but occasionally gradually tapered. In general
appearance a Gangamopteris leaf is similar to that of _Glossopteris
indica_, the chief distinction being the absence of a midrib.
Gangamopteris leaves are on the whole larger than those of
_Glossopteris_; many of them reach a length of 20 cm. and some of
the large Indian fronds are nearly 40 cm. long. The venation of
_Gangamopteris_ shows a greater uniformity in the size and shape
of the meshes than that of _Glossopteris_. The middle of the
lamina, especially in the lower part, is occupied by a few vertical
veins from which branches curve upwards and outwards towards the
edge of the lamina. The secondary veins are connected by frequent
anastomoses and agree very closely with those of _Glossopteris_.
The lamina becomes narrower towards the base, which is either
cuneate or in some cases slightly auriculate (fig. 345).
As I have elsewhere pointed out[1344], the presence or absence of a
midrib is not in itself a character of real taxonomic importance. In
the recent fern _Scolopendrium vulgare_ the frond has a prominent
midrib, while in _S. nigripes_ there is no median rib. Mr Arber has
expressed the opinion that “it is extremely doubtful whether the genus
_Gangamopteris_ should not be merged in _Glossopteris_[1345].” The
retention of the two names is, however, convenient, and it would tend
to confusion were we to carry to its logical conclusion the view that
the recognised distinction between the two genera may not be a mark of
generic difference.
_Gangamopteris_ is confined to Palaeozoic strata, a fact which
leads White[1346] to speak of the Gangamopteris rather than of
the Glossopteris Flora. It occurs in South America, South Africa,
Australia, and India, extending as far north as Kashmir; it has been
discovered by Amalitzky in Permian rocks of Russia[1347]. The Russian
rocks in which _Glossopteris_ and _Gangamopteris_ were found are no
doubt of Permian age. In Australia, South Africa, Brazil and Argentina,
and in the Indian Coal-fields, _Gangamopteris_ is a characteristic
genus of Lower Gondwana rocks. These strata are usually spoken of as
Permo-Carboniferous in order to avoid the danger of attempting on
insufficient data a precise correlation with European formations.
Feistmantel speaks of _Gangamopteris_ as most abundant in the
Talchir-Karharbári beds, though it is represented also in the overlying
Damuda series. In Australia the genus occurs in rocks which correspond
in position and in their plant fossils with the Talchir-Karharbári
beds of India; similarly, in South Africa and South America the
Gangamopteris beds are homotaxial with those of India and Australia.
The leaf described by Carruthers[1348] from Brazil as _Noeggerathia
obovata_ (the type-specimen is in the British Museum) is no doubt
specifically identical with _Gangamopteris cyclopteroides_ Feist.[1349]
In a paper by Mr Hayden on Gangamopteris beds in the Vihi Valley,
Kashmir, evidence is adduced in support of the conclusion that the
rocks are “not younger than Upper Carboniferous and may belong to the
base of that subdivision or even to the Middle Carboniferous[1350].”
It would seem that _Gangamopteris_ was a very widely spread genus
during the latter part of the Carboniferous period in the vast
Southern Continent to which the name Gondwana Land is often applied,
and that it flourished in the Southern Flora during at least part of
the Permian period: with other members of the Glossopteris Flora it
migrated to the North where it has been preserved in Permian rocks of
Northern Russia. The Glossopteris Flora must have had its birth in the
Southern hemisphere. The conclusion seems inevitable that the leaves
of _Glossopteris_ and _Gangamopteris_ in the shales and sandstones of
India, South Africa, South America, and Australia are relics of the
vegetation of a continent of which these regions are the _disjuncta
membra_. Darwin wrote to his friend Hooker in 1881, “I have sometimes
speculated whether there did not exist somewhere during long ages an
extremely isolated continent, perhaps near the South Pole[1351].” It is
probable that _Gangamopteris_ is one of the genera which flourished on
this continent.
_Gangamopteris cyclopteroides_, Feistmantel[1352]. Fig. 345.
1876. Feistmantel, Records Geol. Surv. India, Vol. IX. Pt iii. p. 73.
The specimen represented in fig. 345 illustrates the characters of this
commonest representative of the genus.
[Illustration: FIG. 345. _Gangamopteris cyclopteroides_, Feist. (Nat.
size. From Arber, after Feistmantel.)]
_Gangamopteris kashmirensis_, Seward.
1905. Seward, Mem. Geol. Surv. India, Vol. II. Mem. ii.
This type agrees closely with _G. cyclopteroides_ in size and in the
form of the leaf, but it is distinguished by the flatter form of the
arch formed by the lateral veins, by their greater inclination to the
margin of the lamina, and by the more acutely pointed apex of the
lamina. This species, though not very sharply distinguished from _G.
cyclopteroides_, is important as coming from beds which have been
assigned on other than palaeobotanical evidence to an Upper or possibly
a Middle Carboniferous horizon[1353].
We have no definite information in regard to the nature of the
reproductive organs of _Gangamopteris_, but such evidence as there is
supports the view expressed by Dr White[1354] and shared by some other
authors that _Gangamopteris_ and _Glossopteris_ should be assigned to
the Pteridosperms. Despite the abundance of _Gangamopteris_ leaves,
no fertile specimen has been discovered. This negative evidence
may prove to be as correct as that which led Stur[1355] to exclude
_Neuropteris_, _Alethopteris_ and _Odontopteris_ from the ferns. The
only evidence of a positive kind is that furnished by Dr David White in
his recent Report on the Palaeozoic Flora of South Brazil. This author
describes some small Aphlebia-like leaves under two new generic names
_Arberia_[1356] and _Derbyella_[1357]. The differences between the two
sets of specimens, so far as can be determined from the reproductions
of imperfect impressions, are slight, and it is by no means clear that
a distinction of generic rank exists. These scale-leaves are on the
average about 2 cm. in length; the lamina is oval or rounded and has
more or less prominent lobes. In _Derbyella_ there are indications
of anastomosing veins. The specimens referred to _Arberia minasica_
are, as White points out, very similar to the fossil described by
Feistmantel from Lower Gondwana rocks of India as probably a portion of
an inflorescence of _Noeggerathiopsis_[1358]. Feistmantel’s specimen is
represented in fig. 346: the curled lobes may have originally borne
seeds. In the Brazilian examples the abruptly truncated lobes “bear
evidence of separation from reproductive bodies.” An important point
is the association of these scale-leaves with _Gangamopteris_ fronds
and with gymnospermous seeds of the _Samaropsis_ type. On the leaves
assigned to _Derbyella aurita_ circular depressions occur at the base
of the lobes which are described as probably due to sporangia.
Dr White’s discovery gives us increased confidence in expressing the
view that _Gangamopteris_ bore its reproductive organs on specialised
leaves very different from the sterile fronds; it also strengthens
the suspicion that the genus is a member of the class of seed-bearing
fern-like plants.
[Illustration: FIG. 346. _Arberia_ sp. (= _Noeggerathiopsis_ of
Feistmantel). (Nat. size. After Feistmantel.)]
Lesleya.
This generic designation was instituted by Lesquereux[1359] for
simple oval-linear leaves from the Coal-Measures of Pennsylvania. The
leaves so named are probably generically identical with the specimen
doubtfully assigned by Brongniart[1360] to the Coal-Measures, and
made by him the type of the genus _Cannophyllites_ on the ground of
a resemblance to the leaves of the recent flowering plant _Canna_.
Fig. 347 illustrates the form of a _Lesleya_ leaf from the Coal-basin
of Gard, named by Grand’Eury _L. simplicinervis_[1361], a type in
which the veins are frequently unbranched and not repeatedly forked
as in most examples of the genus (fig. 329, C). The features of the
genus are, the oval-linear or lanceolate shape of the presumably
simple frond, its entire or, in one species at least (_L. Delafondi_,
Zeill.), finely dentate margin, the stout rachis giving off at a very
acute angle numerous dichotomously branched secondary veins. In _L.
Delafondi_ (fig. 329, C), described by Zeiller[1362] from the Lower
Permian of Autun, the frond may reach a length of more than 20 cm. and
a breadth of 8 cm. Similar species are represented by _L. ensis_[1363]
from the coal-field of Commentry, and _L. grandis_[1364] from Upper
Carboniferous rocks of North America. The genus is characteristic of
Upper Carboniferous and Lower Permian strata: the form of the leaf
and the direction of the secondary veins suggest comparison with
_Glossopteris_, but in _Lesleya_ there are no cross-connexions between
the veins. Nothing is known as to the fructification, a fact which
naturally evokes the opinion that the genus is a Pteridosperm[1365]
and not a true fern. Some years before the discovery of Pteridosperms,
Grand’Eury[1366] suggested that _Lesleya_ might be a Gymnosperm; his
opinion being based on the woody nature of the rachis and on the simple
venation of _Lesleya simplicinervis_.
[Illustration: FIG. 347. _Leslya simplicinervis_, Grand’Eury.
(Reduced: after Grand’Eury.)]
Neuropteridium.
In their monograph of fossil plants from the Bunter Series of the
Vosges, Schimper and Mougeot[1367] described some pinnate leaves of
ferns as species of the genus _Neuropteris_. In 1869 Schimper[1368]
placed these in a new sub-genus _Neuropteridium_, in order to draw
attention to the fact that their fronds appear to be simply pinnate
and not bipinnate or tripinnate as in _Neuropteris_. The type-species
of _Neuropteridium_ is _N. grandifolia_ Sch. and Moug. from the
Bunter Sandstones of the Vosges. The genus includes Triassic European
species and the widely distributed Permo-Carboniferous species from
Brazil[1369] originally described by Carruthers as _Odontopteris
Plantiana_. It is probable that some Carboniferous plants, particularly
species from the lower members of the formation, referred to the genus
_Cardiopteris_, are not genetically distinct from the Indian and
southern hemisphere type _Neuropteridium validum_ (= _Odontopteris
Plantiana_).
Fronds pinnate, linear; a broad rachis bears pinnules which may
be either semicircular or broadly linear with an entire or lobed
margin. The longer pinnules may exceed 6 cm. in length. The
pinnules agree with those of _Neuropteris_ in being attached by
the median portion of the lamina and not by the whole base, which
is more or less auriculate. In some cases the repeatedly forked
veins diverge from the centre of the pinnule base; in others there
is a midrib which persists for a short distance only, and in some
species the more persistent median vein gives the segments a closer
resemblance to those of _Neuropteris_. Fructification unknown,
with the exception of obscure indications of sporangia (?) on the
fertile leaves of a Triassic species.
[Illustration: FIG. 348. _Neuropteridium validum_, Feist. Nat. size.
From the Karharbári Coal-field, India. From Arber, after
Feistmantel.]
_Neuropteridium validum._ (Feistmantel[1370]). Fig. 348.
1869. _Odontopteris Plantiana_, Carruthers, Geol. Mag. Vol. VI. p. 9,
Pl. VI. figs. 2, 3.
1878. _Neuropteris valida_, Feistmantel, Mem. Geol. Surv. India,
Foss. Flor. Gondwana Syst., Vol. III. p. 10, pl. II.–VI.
1880. _Neuropteridium validum_, Feistmantel, _Ibid._ 2, p. 84.
The specimen represented in fig. 348 illustrates the main features
of _Neuropteridium validum_. This species is referred to by Dr
White[1371] as _N. Plantianum_ on the ground of priority, and with a
view to perpetuate the name of the English engineer Nathaniel Plant who
discovered the species in a Brazilian Coal-field in the province of Rio
Grande do Sul. Feistmantel’s specific name is however retained as being
much better known. An examination of Mr Plant’s specimen in the British
Museum led me[1372] to speak of the Brazilian species as identical with
_N. validum_ described by Feistmantel from Lower Gondwana rocks of
India. Zeiller[1373] had previously drawn attention to the resemblance
between the two sets of specimens. The frond of _N. validum_ may exceed
50 cm. in length. The lower pinnules may be entire and semicircular in
form while the upper and larger segments, which may reach a length of 5
or 6 cm., are characterised by broad lobes (fig. 348).
This type is represented in the flora of the Talchir-Karharbári series
(Lower Gondwana) of India[1374], in Permo-Carboniferous rocks of Brazil
and Argentine[1375], and in the sandstones of Vereeniging on the
borders of the Transvaal and Cape Colony. It is a characteristic member
of the Glossopteris Flora and occurs in association with _Glossopteris_
and _Gangamopteris_.
_Neuropteridium intermedium_ (Schimper). Fig. 349.
This species has been figured by Schimper and Mougeot[1376] from the
Bunter of the Vosges and more fully described by Blanckenhorn[1377]
from the Bunter beds of Commern. The pinnate leaves reach a length of
65 cm.; the lower semicircular pinnules pass gradually into broadly
linear segments characterised by an auriculate base and a Neuropteris
type of venation (fig. 354, D′, E). In the example reproduced in fig.
349 from one of Blanckenhorn’s figures, the fronds are attached to a
short and thick rhizome bearing roots and portions of old petioles.
[Illustration: FIG. 349. _Neuropteridium intermedium_ (Schimp.). (After
Blanckenhorn. ¼ nat. size.)]
An example of another Triassic species is afforded by _Neuropteridium
grandifolium_ Schimp. and Moug., which agrees very closely with _N.
validum_ in the size and shape of the pinnules. The occurrence in
Lower Mesozoic European rocks of fronds hardly distinguishable from
the older southern species may be regarded as favourable to the view
already expressed, that some at least of the Permo-Carboniferous plants
migrated north of the Equator. The resemblance between the Vosges
Triassic species of _Schizoneura_[1378] and the examples of this genus
recorded from the Lower Gondwana rocks of India affords additional
evidence of a northern migration.
Our knowledge of the reproductive organs of _Neuropteridium_
is practically _nil_. There is no doubt that Zeiller[1379] and
Blanckenhorn[1380] are correct in regarding the Bunter fronds assigned
by Schimper and Mougeot to the genus _Crematopteris_ as the fertile
leaves of _Neuropteridium intermedium_ or some other species from the
same horizon. These fronds bear crowded pinnules similar to those of
_Neuropteridium intermedium_, _N. Voltzii_[1381], and other species,
exhibiting on the exposed surface numerous carbonaceous spots which may
be the remains of sporangia.
Cardiopteris.
Schimper[1382] applied this generic name to Lower Carboniferous
fronds of a simple-pinnate habit which had previously been described
as species of _Cyclopteris_. _Cardiopteris frondosa_ may serve as a
typical example. This species, originally described by Goeppert as
_Cyclopteris frondosa_ (fig. 350), is recorded from Lower Carboniferous
rocks in the Vosges district[1383] in Silesia, Moravia[1384], and
Thuringia[1385]. The pinnules, which are attached in opposite pairs to
a broad rachis, vary in length from 2 to 10 cm. and have a breadth of
2 to 8 cm.; in manner of attachment and venation they agree with those
of _Neuropteridium validum_. The venation is very clearly shown in a
drawing of some large pinnules figured by Stur[1386].
The specimen of _Cardiopteris frondosa_, a portion of which is shown
in fig. 350 on a slightly reduced scale, was originally figured by
Schimper from an unusually good example in the Strassburg Museum.
Schimper’s drawing hardly does justice to the original specimen.
A frond bearing rather narrower pinnules, alternately placed on the
rachis, which Fritsch has described as _Cardiopteris Hochstetterii_
var. _franconica_ from the Culm of Thuringia, bears a close resemblance
to _Neuropteridium validum_ but differs in the entire margin of the
pinnules. An Upper Carboniferous species from Russia described by
Grigoriew[1387] as _Neuropteris_, cf. _cordata_ var. _densineura_,
represents another form of similar habit.
[Illustration: FIG. 350. _Cardiopteris frondosa_ (Goepp.). (¾ nat.
size. After Schimper.)]
Schuster[1388] has recently proposed a new generic name _Ulvopteris_
for a fragment of a pinna from the Coal-Measures of Dudweiler in
Germany bearing large pinnules, which he compares with those of
_Cardiopteris_ and species of _Rhacopteris_. The specimen appears to be
indistinguishable from some of those already referred to as conforming
to _Neuropteridium_, and it is difficult to recognise any reason for
the creation of a new generic name.
We cannot hope to arrive at any satisfactory decision in regard to the
precise affinity between _Neuropteridium validum_ and species referred
to _Cardiopteris_ and other genera so long as portions of sterile
fronds are the only tests at our disposal. It is difficult to determine
whether a specimen consisting of an axis bearing pinnules represents a
large pinna of a bipinnate frond or if it is a complete pinnate leaf.
There is, however, no adequate reason for supposing that the presumably
pinnate fronds from the Gondwana Land rocks are generically distinct
from the Lower Carboniferous European species _Cardiopteris frondosa_.
Granting the probability that both genera are Pteridosperms and
closely allied to one another, the two generic names may be retained
on the ground of long usage and in default of satisfactory evidence
confirmatory of generic identity. _Cardiopteris_ would thus stand for
a type of frond characteristic of the Lower Carboniferous strata of
Europe, while _Neuropteridium_ is retained for the Southern species _N.
validum_, and for others from the Trias of the Vosges.
Aphlebia.
This name was proposed by Presl[1389] for large leaf-like impressions
having a pinnate or pinnatifid form and characterised by a confused
irregular type of venation, or by a fine superficial striation or
wrinkling which simulates veins. Gutbier had previously described
similar fossils as _Fucoides_, and other authors have described
Aphlebiae as species of _Rhacophyllum_, _Schizopteris_, and other
genera[1390]. The term _Aphlebia_ is retained, not as denoting a
distinct genus but (i) as a descriptive name for detached leafy
structures similar to those figured by Presl, which are now recognised
as laminar appendages of the petioles of ferns or fern-like fronds, and
(ii) as an epithet for highly modified pinnules which frequently occur
at the base of the primary pinnae of Pecopteroid and Sphenopteroid
fronds (e.g. _Dactylotheca plumosa_, fig. 293)[1391].
Modified pinnules, similar in their reduced and deeply dissected
lamina to those represented in fig. 293, are frequently found at the
base of the primary pinnae of Palaeozoic species of _Sphenopteris_
and other genera of Pteridosperms or ferns, including members of
the Coenopterideae. Potonié[1392] gives a list of various types of
Aphlebiae in his paper on these organs. A striking case has recently
been described by Zeiller in a French Upper Carboniferous species,
_Sphenopteris Matheti_[1393]. It would seem that the larger examples of
Aphlebiae are more frequently associated with the compound leaves of
Pteridosperms than with those of Ferns[1394].
As examples of the larger types of Aphlebiae reference may be made to
_Aphlebia crispa_ (Gutb.)[1395], which reaches a length of nearly 60
cm. and has the form of a more or less triangular pinnate leaf divided
into decurrent deeply lobed segments, to a similar species represented
by _A. Germari_ (= _Schizopteris lactuca_ Germ.)[1396] which simulates
the leaves of endive (_Cichorium endivia_ L.), and to some large forms
figured by Grand’Eury[1397] as species of _Schizopteris_.
Aphlebiae such as that figured by Kidston[1398] as _Rhacophyllum
crispum_, with narrow ultimate segments, might easily be mistaken for
the impressions of an alga.
The term _Aphlebia_ may be applied also to the Cyclopteroid pinnules
on the petioles of some species of _Neuropteris_, _Odontopteris_
and _Archaeopteris_. Goebel[1399] has referred to the application
by Potonié and other authors of the term Aphlebioid to the pinnules
which serve as bud-protecting organs in recent fronds of _Gleichenia_
(fig. 226, p. 290); he expresses the opinion that it is superfluous
and misleading to make use of a special designation for structures
which are undoubtedly modified pinnules. In the case of fossils it is,
however, convenient to employ the term _Aphlebia_ as a descriptive
name for modified pinnules or stipular structures which cannot
be connected with definite species of fronds. It is clear that
some Aphlebiod leaflets, such as those of _Dactylotheca_, served
as protective organs for the unexpanded pinnae[1400], and in all
probability the large Aphlebiae served the same purpose as the fleshy
stipules of _Angiopteris_ and _Marattia_ which cover the uncoiled
fronds. The pinnatifid scale-leaves of considerable size (fig. 351)
which occur in the leaf-axils or as ochrea-like stipules on the fronds
of _Gunnera_ (a tropical and subtropical Dicotyledonous genus) bear a
very close resemblance to some Palaeozoic Aphlebiae, e.g. _Aphlebia
crispa_ (Gutb.). The recent and fossil scale-leaves may be regarded as
similar in function as in form; moreover the delicate coiled fronds
of Palaeozoic Pteridosperms or ferns, like those of some recent
flowering plants, may have been kept moist by a secretion of mucilage.
The pinnatifid stipules of _Marattia fraxinea_ (fig. 241, B, p. 317)
resemble certain fossil Aphlebiae, and the wrinkled surface of the
recent stipules presents an appearance similar to that which in some
fossil forms has been erroneously described as veining. It is not
improbable that mantle-leaves of such recent ferns as _Polypodium
quercifolium_ (fig. 234, M, p. 303) are comparable with some fossil
Aphlebiae which may have served as humus-collectors for Palaeozoic
epiphytes.
[Illustration: FIG. 351. Scale-leaf of _Gunnera manicata_. (Slightly
reduced. M.S.)]
The filiform appendages on the petioles of the recent fern _Hemitelia
capensis_ (fig. 235, p. 304) have often been compared with the
aphlebioid leaflets of fossil fronds.
Potonié who has discussed the nature of Aphlebiae regards them as
vestiges of a once continuous lamina, which formed a winged border to
the branched axes of more primitive forms of fronds. It is possible
that the pinnules between the pinnae on the rachis of _Archaeopteris_
and the Cyclopteroid leaflets of _Neuropteris_ and _Odontopteris_ may
have the morphological significance attributed to them by Potonié. In
some cases it is probable that the Aphlebiae, whether vestiges or not,
served the purpose of protecting either the whole frond or individual
pinnae. Aphlebiae, though especially characteristic of Palaeozoic
leaves, are occasionally met with in the form of modified pinnules at
the base of the primary pinnae on Mesozoic ferns, e.g. in _Coniopteris
hymenophylloides_[1401].
In some fern fronds the lowest pinnule of each pinna differs in shape
or size from the normal ultimate segments, but it would be almost
affectation to extend the use of the term _Aphlebia_ to such pinnules.
The Jurassic species _Cladophlebis lobifolia_ (Phill.) is a case
in point[1402]. In this fern, which some authors speak of, without
sufficient reason, as _Dicksonia lobifolia_[1403], the lowest pinnule
is large and different in shape from the others.
[Illustration: FIG. 352.
A. _Sphenopteris obtusiloba_. Pinnule. (Enlarged. After Zeiller.)
B, C. _S. obtusiloba_. (⅞ nat. size. After Zeiller.)
D. _Pecopteris arborescens_. (Slightly enlarged. After Zeiller.)
E. _Sphenopteris furcata_ (= _Diplotmema furcatum_). (Slightly
enlarged. After Zeiller.)]
Sphenopteris.
_Sphenopteris_ is one of the many generic names which we owe to
Brongniart[1404]. It is the generic designation used for a great number
of Palaeozoic and later fronds, most of which are those of true ferns
while some Palaeozoic species are undoubted Pteridosperms. The genus,
which is purely provisional, includes members of widely different
families possessing pinnules of the same general type, such as is
represented in some recent species of _Davallia_, _Asplenium_, and
other ferns.
The fronds of _Sphenopteris_ may be bipinnate, tripinnate, or
quadripinnate; the rachis may be dichotomously branched or the
branching may be of the pinnate type characteristic of most recent
ferns. The pinnules are small; they vary considerably in shape even
in a single frond, but the chief characteristics are: the lobed
lamina, contracted and often wedge-shaped at the base (fig. 352),
the dichotomously branched veins radiating from the base or given
off from a median rib at an acute angle. The lamina may be divided
into a few bluntly rounded lobes (fig. 352, C) or deeply dissected
into linear or cuneate segments (fig. 352, A, B, E).
Examples of Sphenopteroid leaves have already been described under
the genera _Coniopteris_, _Onychiopsis_, _Ruffordia_, etc. Among the
numerous examples of _Sphenopteris_ species from the Carboniferous
rocks mention may be made of _Sphenopteris obtusiloba_ Brogn.[1405]
(fig. 352, A–C), which occurs in the Middle and Lower Coal-Measures
of Britain[1406]. This type is characterised by the almost orbicular,
oval or triangular pinnules which may reach a length of 15 mm.; they
are occasionally entire, but more usually divided into 3 to 5 rounded
lobes. The forked veins radiate from the base of the pinnule. The
rachis may be dichotomously branched. Fructification unknown.
The species _S. furcata_ Brongn.[1407], characteristic of the Middle
and Lower Coal-Measures of Britain (fig. 352, E), is referred to under
Stur’s genus _Diplotmema_[1408] in which it is included by some authors
solely because of the dichotomous habit of branching of the pinnae.
The pinna represented in fig. 353 illustrates a similar type of
pinnule. This species, which is very common in the Calciferous
Sandstone of Scotland, was described by Lindley and Hutton as
_Sphenopteris affinis_[1409].
The fronds of _Sphenopteris affinis_ were discovered by Mr
Peach[1410] in a fertile condition, but he regarded the reproductive
organs as those of a plant parasitic on the _Sphenopteris_ fronds.
Kidston[1411] substituted Stur’s genus _Calymmatotheca_ for
_Sphenopteris_ on the ground that the sporangia figured by Peach
under the name _Staphylopteris Peachii_ bear a close resemblance
to the organs which Stur described as valves of an indusium in his
species _Calymmatotheca Stangeri_[1412]. An examination of Stur’s
specimens by Miss Benson[1413] and by Prof. Oliver and Dr Scott has
confirmed Stur’s interpretation of the appendages at the tips of the
fertile pinnae as valves of an indusial or cupular structure. The
superficially similar bodies on the fertile pinnae of _S. affinis_
are however true sporangia, and cannot legitimately be included in
the genus _Calymmatotheca_ as described by Stur. For this reason
Miss Benson institutes a new genus _Telangium_, the type-species
of which, _T. Scotti_ from the Lower Coal-Measures of Lancashire,
is based on petrified material. The Scotch species _Sphenopteris
affinis_ (= _Calymmatotheca affinis_ of Kidston) is also transferred
to _Telangium_; the sporangia are considered by Miss Benson to be
microsporangia. This with other species is no doubt correctly included
in the Pteridosperms. A complete frond of _Sphenopteris affinis_,
showing a regular dichotomy of the main axes, is represented by an
admirable drawing in Hugh Miller’s _Testimony of the Rocks_[1414].
[Illustration: FIG. 353. _Sphenopteris affinis_, Lind. and Hutt. From
the Calciferous Sandstone of Burdiehouse (Scotland). (Sedgwick
Museum, Cambridge.) M.S.]
Some of the Palaeozoic species of _Sphenopteris_ probably represent
the fronds of true ferns, but others are known to have been borne
by Pteridosperms. _S. Hoeninghausi_ (fig. 290, C, p. 399) is the
foliage of _Lyginodendron_, and Scott[1415] speaks of three species,
_S. dissecta_, _S. elegans_, and _S. Linkii_ as the leaves of
_Heterangium_. Grand’Eury[1416] has recorded the occurrence in French
Coal-Measures of seeds in association with other Sphenopteroid fronds.
Mariopteris, Diplotmema, Palmatopteris.
The discovery of sporangia on the fronds of several Palaeozoic species
of _Sphenopteris_ and _Pecopteris_ has led to the institution of new
generic names, which indicate an advance in knowledge beyond the stage
implied by the use of those provisional designations based solely on
the form and venation of the pinnules. Other names have been created by
authors in place of _Sphenopteris_ and _Pecopteris_ on the ground that
a striking feature in the mode of branching of fronds is sufficiently
important to justify generic recognition even in the absence of
fertile specimens. As examples of designations based primarily on
the branch-system of compound leaves, the genera _Mariopteris_,
_Diplotmema_, and _Palmatopteris_ may be briefly considered (fig. 354
A–C). Dr Kidston[1417] is of opinion that the creation of new genera
for purely vegetative characters of fronds is of no real advantage, and
he prefers to retain the older provisional names for species known only
in the sterile condition. On the other hand, if we are sufficiently
familiar with specimens large enough to enable us to recognise a
well-defined morphological character, it may serve a useful purpose to
employ a generic designation for features which may have a phylogenetic
value. A comparative examination of Palaeozoic, Mesozoic, and recent
compound fronds, including both Pteridosperms and true ferns, brings
to light certain distinguishing features characteristic of the older
types which, as Potonié maintains[1418], point to the derivation of
the pinnate habit from a primitive dichotomous system of branching.
For a more complete discussion of this question reference should be
made to Potonié’s suggestive papers. Among recent ferns _Matonia_ and
_Dipteris_, two survivals from the past, afford instances of fronds
with a branching system of the dichotomous type.
Similarly, in _Gleichenia_, _Lygodium_, and more rarely in species of
Polypodiaceae (_e.g._ _Davallia aculeata_, fig. 232) dichotomy is a
striking feature of the fronds. In the great majority of recent ferns
the fronds have assumed a pinnate habit. Among Palaeozoic fern-like
fronds dichotomous branching of the main rachis and of the pinnae is
much more common. Potonié draws attention to several other features
which distinguish Palaeozoic fronds from the majority of later species:
the frequent occurrence of pinnules borne directly on the main rachis
(fig. 354, D), and of modified pinnules or Aphlebiae on the rachis
and petiole, are characters to which he attributes an evolutionary
significance. The main point is that a comparative examination of
leaf-form affords evidence in favour of the view that the modern type
of frond, with its naked rachis bearing two rows of pinnae, has been
derived from a less specialised type in which the distinction between
the parts of the leaf is much less evident. The primitive leaf was
probably a dichotomously branched axis provided with a continuous
lamina which eventually became broken up into separate lobes or
pinnules.
As the dichotomy of the frond became less regular, a pinnate habit was
acquired, as is clearly seen in many Palaeozoic types which constitute
connecting links between forked and pinnate fronds (fig. 354, D). The
Aphlebiae may be remnants of the once-continuous lamina on the petiole,
and the normal pinnules borne on the rachis may be regarded as the
attributes of fronds in which the division of physiological labour had
not reached the stage which characterises the leaves of recent ferns.
_Mariopteris._
This name, which is due to Zeiller[1419], is applied by him to
Palaeozoic fronds characterised by a double bifurcation of the rachis
of the primary pinnae. _Mariopteris muricata_ (= _Pecopteris muricata_
Schloth.) may be taken as the type of the genus. This species is
common in the Lower and Middle Coal-Measures of Britain and rare
in the Upper Coal-Measures[1420]. It is described by Kidston[1421]
as one of the most polymorphic and widely distributed Coal-Measure
species. The pinnules as seen in fig. 364, B, are of the Sphenopteroid
type. No fertile specimens are known, but it is significant that
Grand’Eury[1422] has recorded the association of _Mariopteris muricata_
and seeds.
The main rachis gives off alternate naked branches, each of which
bifurcates at its apex into two short naked axes, and these are again
forked, the ultimate branches having the form of bipinnate pinnae
provided with large Sphenopteroid pinnules (fig. 354, B). Zeiller
includes in _Mariopteris_ some species which Stur[1423] referred to
his genus _Diplotmema_. Possibly some of the Palaeozoic fronds with a
zigzag rachis may have been climbers like _Lygodium_.
[Illustration: FIG. 354.
A. _Palmatopteris._
B. _Mariopteris._ (A, B, after Potonié.)
C. _Diplotmema Zeilleri_, Stur. (After Zeiller.)
C′. _D. Zeilleri._ Pinnule. (× 3. After Zeiller.)
D. _Neuropteris macrophylla._ (British Museum.)
D′. _N. macrophylla._ Pinnule. (Slightly enlarged. After Kidston.)
E. _N. heterophylla._ Pinnule. (Slightly enlarged. After Zeiller.)
F. _N. Scheuchzeri._ (Slightly reduced. After Kidston.)
G. _Alloiopteris Essinghii._ (Enlarged. After Potonié.)]
_Diplotmema._
This generic name is employed by Zeiller[1424] and other authors in
a more restricted sense than that in which it was originally used by
Stur. The Upper Carboniferous species _Sphenopteris furcata_ Brongn.
(fig. 352, E) may serve as the type. This species occurs in the Middle
and Lower Coal-Measures of Britain[1425]. The main rachis gives off
branches as in _Mariopteris_, but in _Diplotmema_ each naked lateral
branch is forked at its apex into two opposite pinnae bearing deeply
dissected Sphenopteroid pinnules. Zeiller[1426] and Stur have recorded
fertile specimens of _Diplotmema_, but in no case have actual sporangia
been discovered. In the species _Diplotmema Zeilleri_ Stur (fig. 354,
C, C′) two Aphlebiae occur at the base of each secondary axis[1427].
It has been pointed out by Potonié that in _Diplotmema furcatum_ the
equal dichotomy of the lateral branches is not characteristic of the
frond as a whole. In the case of branches higher on the rachis the
dichotomy becomes unequal and the forked axis is gradually replaced by
a simple pinna (fig. 354, A). For this type of frond, Potonié proposed
the generic name _Palmatopteris_ in place of _Diplotmema_, which
he discards. The long comparatively slender rachis of _P. furcata_
suggests comparison with the liane species of _Lygodium_[1428].
[Illustration: FIG. 355.
A. _Cephalotheca mirabilis_, Nath. Fertile pinnae. (Partially
restored. After Nathorst.)
B. _C. mirabilis._ Sterile pinnule. Nat. size. (After Nathorst.)]
Cephalotheca.
This genus was proposed by Nathorst[1429] for some peculiar bipinnate
fertile fronds from the Upper Devonian rocks of Bear Island. The pinnae
bear slender forked ultimate segments represented by a few detached
fragments (fig. 355, B), associated with the rachises. The fertile
pinnae are given off in opposite pairs from the main axis over which
they are concrescent (fig. 355, A). A mop-like cluster of sporangia is
borne on the lower surface and close to the base of a fertile pinna:
the exannulate sporangia are compared with those of _Scolecopteris_.
Nathorst compares _Cephalotheca_ with a Belgian species of Upper
Devonian age described by Crépin[1430] as _Rhacophyton condrusorum_ and
by Gilkinet[1431] as _Sphenopteris condrusorum_. A similar fossil is
also described by Baily[1432] as _Filicites lineatus_ from the Kitorkan
Grits of Ireland.
The position of _Cephalotheca_ cannot be definitely determined from
the available data, but it is more probable that it was a seed-bearing
Pteridosperm and not a true fern. Zeiller[1433] has recently expressed
the same opinion.
Thinnfeldia.
The genus _Thinnfeldia_, founded by Ettingshausen in 1852[1434] on
some Hungarian Liassic specimens, though frequently included in the
Filicales, cannot be said to occupy that position by virtue of any
well-authenticated filicinean features. It is by no means improbable
that many of the species referred to this genus are closely allied to
Palaeozoic Pteridosperms.
_Thinnfeldia_ may be briefly defined as follows:
Fronds simple and pinnatifid, pinnate or bipinnate: rachis broad
and occasionally dichotomously branched. Pinnules often fleshy or
coriaceous; broadly linear, entire or lobed, provided with a midrib
from which simple or forked secondary veins are given off at an
acute angle: or the laminae may be short and broad without a midrib
and traversed by several slightly divergent and forked veins.
No satisfactory evidence of reproductive organs has so far been
adduced.
The genus is chiefly characteristic of Upper Triassic, Rhaetic, and
Jurassic floras, though it was in all probability represented in
Permian floras. Several species, many of which are valueless, are
recorded also from Cretaceous and Tertiary formations. Search should
be made for fertile specimens or for evidence as to the association of
seeds with _Thinnfeldia_ fronds.
Some Permian fossils from Kansas which Sellards[1435] has made the
type of a new genus, _Glenopteris_, appear to be indistinguishable
generically from leaves of Lower Mesozoic age universally recognised as
typical examples of _Thinnfeldia_.
_Thinnfeldia odontopteroides_ (Morris)[1436]. Figs. 356–358.
This is a very variable species as regards the shape and size of
the ultimate segments and their venation. It is a type of extended
geographical range characteristic of Rhaetic or Upper Triassic rocks
in Australia, South Africa, India, South America, and various European
localities.
Frond bipinnate; the broad rachis may be dichotomously branched.
Pinnules with a thick lamina which may be almost semicircular in
form, deltoid, broadly oval or broadly linear, and often confluent
at the base. Short and broad pinnules occur on some fronds directly
attached to the main rachis between the pinnae. The longer and
narrower pinnules (fig. 356, C), resembling those of the Palaeozoic
genus _Alethopteris_, have a well-defined midrib, while the smaller
segments are characterised by several slightly divergent veins
which spring directly from the rachis (fig. 356, A). Epidermal
cells polygonal or, above the veins, rectangular in shape; stomata,
which are slightly sunk, occur on both the upper and lower
epidermis. Fertile specimens unknown.
The portion of a lobed pinnule shown in fig. 356, B, illustrates a
form of segment intermediate between the linear type with a midrib
and a row of shorter pinnules without a median vein. Fig. 356, D,
represents another instance of variation in the arrangement of the
veins in segments of different sizes. Various specific and generic
names have been assigned to Thinnfeldia fronds of Rhaetic age on the
ground of the occurrence of pinnules longer and narrower than those
usually associated with _T. odontopteroides_; but in view of the range
of variation met with in a single leaf it is advisable to extend rather
than to restrict the boundary of what we are pleased to regard as a
specific type.
[Illustration: FIG. 356.
A–D. _Thinnfeldia odontopteroides_ (Morris).
E. _Ptilozamites._ (E, after Nathorst.)]
The name _Thinnfeldia lancifolia_ has been applied by Morris to fossils
from Australia which may be identified with _T. odontopteroides_,
and the same designation is employed by Szajnocha and by
Solms-Laubach[1437] for Rhaetic specimens from South America. Similar
fronds are described by Geinitz[1438] as _Thinnfeldia tenuinervis_
from Argentine Rhaetic strata. _Odontopteris macrophylla_ Curran, _T.
falcata_ Ten.-Woods, _Gleichenia lineata_ Ten.-Woods, and _Cardiopteris
Zuberi_ Szaj. afford other examples of what are probably closely allied
forms[1439].
[Illustration: FIG. 357. _Thinnfeldia odontopteroides_ (Morris).
⅘ nat. size.]
Some exceptionally large examples of _T. odontopteroides_ are figured
by Feistmantel[1440] from the Hawkesbury series of New South Wales in
which the bipinnate frond has a breadth of 25–30 cm. A specimen from
the Molteno beds of South Africa, probably of Rhaetic age, represented
in fig. 357, illustrates a smaller leaf with pinnules of the linear
type, some of which are partially divided into shorter pinnules with
forked veins. The example represented in fig. 358, from Cyphergat (S.
Africa), shows two equal branches of a rachis with small contiguous
segments.
[Illustration: FIG. 358. _Thinnfeldia odontopteroides_. From a specimen
in the British Museum (v. 2490). 1½ nat. size.]
Some specimens figured by Zeiller[1441] from the Rhaetic strata
of Tonkin as _Pecopteris (Bernouillia?_) sp. may be portions of
_Thinnfeldia_ fronds, and the large leaves which he refers to
_Ctenopteris Sarreni_ differ but slightly from the Australian specimens
described by Feistmantel as _T. odontopteroides_.
_Thinnfeldia rhomboidalis_, Ettingshausen. Figs. 359, 360, C.
Under this name Ettingshausen described the type-specimen of the genus
from Lower Lias strata at Steierdorf in Hungary. He assigned the plant
to the Coniferae on the ground of a resemblance of the pinnules to
the phylloclades of _Phyllocladus. Thinnfeldia rhomboidalis_ bears a
close resemblance to _T. odontopteroides_, but the pinnules are usually
longer and narrower, as shown in the English specimen from the Lower
Lias of Dorsetshire represented in fig. 359. The darker margin of the
pinnules shown in fig. 360, C, gives the impression of a revolute
lamina, but a microscopical examination points to a thicker cuticle at
the edge of the segments.
[Illustration: FIG. 359. _Thinnfeldia rhomboidalis_, Ettings. Slightly
reduced. From an English Liassic specimen in the British Museum.
[M.S.]]
The species is recorded from Jurassic rocks of France, Germany, Italy,
India, Australia, and elsewhere[1442].
Palaeobotanical literature contains numerous records of Jurassic,
Cretaceous and some Tertiary species referred to _Thinnfeldia_,
but many of these are probably not generically identical with _T.
odontopteroides_ or _T. rhomboidalis_. Mr Berry[1443] in a paper on
_The American species referred to Thinnfeldia_ concludes that the genus
is “a rather indefinite one ... and badly in need of revision.” He
regards the Middle and Upper Cretaceous American species as Conifers
related to _Phyllocladus_ and probably forming a link between the
Podocarpeae and Taxeae: for these forms he proposes the generic name
_Protophyllocladus_. The opinion has been expressed elsewhere[1444]
that this “problematical[1445]” genus rests on an unsatisfactory basis;
the available data do not justify the use of a name which implies the
existence in North American Cretaceous floras of a type related to
the New Zealand and Tasmanian Conifer _Phyllocladus_. We are not in a
position to assign a single species of _Thinnfeldia_ to the Filicales
or the Gymnosperms.
A leaflet from Jurassic rocks of Poland figured by Raciborski[1446]
shows what this author regards as the impression of a circular sorus:
no sporangia have been found. A specimen in the British Museum[1447],
which is said to come from Rhaetic beds in Queensland, shows a row
of contiguous polygonal prominences on each side of the midrib which
resemble the sori of a fern; but until sporangia are discovered we
cannot determine the precise nature of this apparently fertile frond.
A species described by Fontaine[1448] from the Potomac beds
(Wealden-Jurassic) of North America as _Thinnfeldia variabilis_ affords
a good example of a plant which cannot be identified with any degree
of confidence either as a fern or a seed-bearing type. Mr Berry draws
attention to the former application of this name by Velenovský to a
distinct Lower Cretaceous Bohemian species and proposes for Fontaine’s
plant the name _T. Fontainei_; he maintains that no one has doubted
the fern-nature of the Potomac plant. _T. variabilis_ may indeed be a
fern, but the evidence is not such as to preclude legitimate doubts
as to the correctness of this suggestion. Solms-Laubach[1449], in
referring to Schenk’s view that _Thinnfeldia_ and its allies may
represent a group intermediate between Ferns and Gymnosperms, admits
that it is a possible supposition; he is, however, inclined to consider
_Lomatopteris_ and _Cycadopteris_, “genera especially comparable with
_Thinnfeldia_” as more probably ferns.
At this point we may conveniently consider a series of genera which
occupy an equally uncertain position and bear a very close resemblance
to _Thinnfeldia_.
[Illustration: FIG. 360.
A. _Lomatopteris jurensis_. (⅞ nat. size. After Kurr.)
B. _L. Schimperi_. (⅞ nat. size. After Salfeld.)
C. _Thinnfeldia rhomboidalis_, Ett. (Slightly enlarged. British
Museum. No. 52672.)]
Lomatopteris.
The generic name _Lomatopteris_ was proposed by Schimper[1450] for some
bipinnate fronds originally described by Kurr[1451] from Jurassic rocks
of Württemberg as _Odontopteris (?) jurensis_ (fig. 360, A). I have
elsewhere expressed the opinion[1452] that this German species may be
identical with _Thinnfeldia rhomboidalis_ Ett. Kurr’s type-specimen,
a portion of which is reproduced in fig. 360, A, consists of a frond
or large pinna characterised by a prominent and broad rachis giving
off alternate linear pinnae bearing bluntly rounded, contiguous and
basally concrescent pinnules having a thick or revolute border and a
central rib. The lateral veins are visible in the ultimate segments
of Kurr’s fossil. Saporta[1453] has described several species, which
he refers to Schimper’s genus, from French Jurassic strata: it is,
however, difficult to recognise some of the examples represented in his
illustrations as specifically distinct forms. This author notices the
resemblance of _Lomatopteris_ to _Thinnfeldia_, not only in habit but
in the structure of the epidermal cells[1454]. In _Lomatopteris_ and
in _Thinnfeldia_ the cells have straight and not sinuous walls and the
slightly sunken stomata are surrounded by a ring of epidermal cells.
Salfeld[1455] has recently described portions of fronds from Jurassic
rocks of South-West Germany, which he identifies as _Lomatopteris
jurensis_. He disagrees with my view that _Lomatopteris_ does not
differ sufficiently from _Thinnfeldia_ to be accorded generic autonomy,
chiefly on the ground that the folded-over edge of the pinnules is
a distinguishing feature of _Lomatopteris_. There is, however, no
difference, in appearance at least, between the leaflets of some
species of _Thinnfeldia_, e.g. _T. rhomboidalis_ from Liassic rocks of
England[1456], and those referred to _Lomatopteris_. In a later paper,
Salfeld[1457] describes some Portlandian fragments from North Germany
as _Lomatopteris Schimperi_, identifying them with a Wealden fossil
of somewhat doubtful affinity, which Schenk[1458] makes the type of
his species. The Portlandian specimens are described as tripinnate,
with thick decurrent obtusely terminated pinnules with a revolute
edge. The general form of the frond is very similar to that of _L.
jurensis_. Salfeld publishes a photograph of a large specimen which he
describes as fertile and a drawing of a piece of a pinna: the latter
is reproduced in fig. 360, B. He speaks of sori occurring in two rows,
probably attached to lateral veins, in the groove between the midrib
and the revolute edge of the lamina. The sporangia are described as
“nicht näher bekannt[1459].” An examination of the figures reveals
nothing as to the nature of the “sori.” The specimens are considered
by Salfeld to afford decisive evidence against the view that
_Lomatopteris_ and _Thinnfeldia_ are generically identical. Nothing has
so far been published which constitutes a valid argument in favour of
retaining Schimper’s generic name.
Cycadopteris.
Zigno[1460] founded the genus _Cycadopteris_ on Italian Jurassic
impressions regarded by Schimper as indistinguishable from
_Lomatopteris_. As Solms-Laubach[1461] points out, the supposed sori
of _Cycadopteris_ described by Zigno are not convincing. There appear
to be no satisfactory reasons for separating _Cycadopteris_ from
_Lomatopteris_, nor do the fronds described under these names exhibit
any important differences from _Thinnfeldia_.
Ptilozamites.
Nathorst[1462] founded this genus on a remarkable series of
specimens from the Rhaetic Coal-beds of Scania and assigned it to
the Cycadophyta. The species _Ptilozamites Heeri_ may be taken as a
representative type. The leaves are linear and simply pinnate. In the
example shown on a much reduced scale in fig. 361 the frond is 53 cm.
long and 2·1 cm. broad. The upper edge of each pinnule is straight or
slightly concave; the lower edge is rounded; the veins are slightly
divergent and dichotomously branched (fig. 356, E, p. 539). In some of
Nathorst’s specimens the broad rachis is forked as in many Thinnfeldias.
As a comparison of fig. 356, A and E, shows, the pinnules of some
specimens of _Thinnfeldia odontopteroides_ are identical with those of
_Ptilozamites_. In the latter genus the rachis is either unbranched
or occasionally forked, while in _Thinnfeldia_ the branching may be
of the dichotomous or pinnate type. In _Ptilozamites_ the segments
appear to be always without a midrib, while a median vein frequently
occurs in those of _Thinnfeldia_. There can be little doubt as to the
very close alliance between the Rhaetic species referred to these two
genera. The name _Ptilozamites_ should perhaps be retained for such
long and narrow fronds as that shown in fig. 361: no species included
in _Thinnfeldia_ is known in which the rachis reached so great a length
without branching. The habit of _Ptilozamites Heeri_ predisposes one in
favour of Nathorst’s opinion that the fronds are Cycadean: we have no
information in regard to the nature of the reproductive organs.
[Illustration: FIG. 361. _Ptilozamites Heeri_, Nath. (⅓ nat. size.
After Nathorst.)]
Ctenopteris.
This name was instituted by Saporta[1463], at Brongniart’s
suggestion, for Liassic species characterised by pinnules like those
of _Thinnfeldia_, but distinguished by the bipinnate habit of the
frond. Saporta compares the genus with the Palaeozoic leaves known as
_Odontopteris_, and with Italian Jurassic plants referred by Zigno to
his genus _Dichopteris_.
The name _Ctenozamites_ is applied by Nathorst[1464] to the type of
frond which Saporta, Zeiller, and other authors refer to _Ctenopteris_.
Nathorst instituted _Ctenozamites_ for fossils agreeing in the form and
venation of the pinnules with his genus _Ptilizamites_ but differing in
being bipinnate and not pinnate.
Fronds of _Ctenopteris_ are characteristic of the Jurassic and Rhaetic
series; they are known only in the sterile condition. As Zeiller[1465]
says, _Ctenopteris_ may be a member of the Cycadofilices, an extinct
group founded on Palaeozoic plants combining Cycadean and Filicinean
characters, and some of which are now known to be Pteridosperms. It is
probable that the genus is not a true fern: it is more likely to be a
member of the Cycadophyta or of some generalised extinct group.
_Ctenopteris cycadea_ (Brongniart). Fig. 362.
1828. _Filicites cycadea_, Brongniart, Hist. Vég. foss. p. 387, Pl.
CXXIX.
1832. _Odontopteris cycadea_, Berger, Verstein. Coburg Geg. p. 23,
Pl. III.
1873. _Ctenopteris cycadea_, Saporta, Pal. Franç. Vol. I. p. 355,
Pls. XL. XLI.
Frond bipinnate, broad rachis giving off branches at an acute
angle; pinnules broadly linear, slightly falcate, with several
slightly divergent forked veins.
A frond very similar to the Lower Lias specimen from Dorsetshire
represented in fig. 362 was described by Leckenby as _Ctenis Leckenbyi_
(Bean MS.) from the Inferior Oolite of Yorkshire[1466]. Leckenby
recognised the possibility of a Cycadean affinity, but regarded
the bipinnate habit as an objection. The branched fronds of the
Australian Cycad _Bowenia_ supply an answer to this objection. Several
good examples of _Ctenopteris cycadea_ are figured by Schenk[1467]
from Rhaetic rocks of Persia. Zeiller’s Tonkin Rhaetic species, _C.
Sarrani_[1468], affords a striking illustration of the difficulty of
drawing a clear line of separation between _Ctenopteris_ and some
species of _Thinnfeldia_.
[Illustration: FIG. 362. _Ctenopteris cycadea_, Brongn. (½ nat. size.)
From a specimen in the British Museum. [M.S.]]
_Ctenopteris_ is in all probability very closely related to
_Thinnfeldia_ and _Ptilozamites_.
Dichopteris.
This genus was proposed by Zigno[1469] for some large specimens from
the Jurassic plant-beds of Northern Italy.
The bipinnate leaves are characterised by the great breadth of the
rachis which is dichotomously branched in the distal region (fig.
363); the linear pinnae reach a considerable length. Pinnules
relatively small, oblong and slightly contracted at the base; the
decurrent and confluent lamina forms a narrow wing to the main
axis. Veins slightly divergent and forked, as in _Ptilozamites_.
_Dichopteris visianica_, Zigno. Fig. 363.
A specimen of this species in the Padua Museum has a total length of
83 cm. It has been elsewhere suggested[1470] that a fragment figured
by Zigno as a fertile example of this type is probably part of a frond
of the Osmundaceous fern _Todites_. Since this opinion was expressed I
have had an opportunity of examining the actual specimen at Padua: the
circular patches described by Zigno as sori appear to be irregularities
in the matrix and not an original feature.
Brongniart[1471] instituted the genus _Pachypteris_ for some
imperfectly preserved English Jurassic fossils from Whitby, which he
described as _P. lanceolata_. Specimens have since been described[1472]
from the Inferior Oolite rocks of the Yorkshire coast. Brongniart
described the pinnules as being without veins or as possessing only a
midrib. It is almost certain that the apparent absence of veins in most
specimens[1473] is due to the fleshy nature of the segments and that
the species _P. lanceolata_ should be transferred to _Dichopteris_.
Krasser[1474] has described a species from Cretaceous rocks of the
island of Lesina, off the Dalmatian coast, as _Pachypteris dalmatica_
which is very similar in habit to the English specimens and to Zigno’s
_Dichopteris visianica_. One of Krasser’s specimens is practically
identical with _Dichopteris lanceolata_ (Brongn.), while in others
the small pinnules are replaced in some of the pinnae by a continuous
lamina with a few distal serrations. The latter form a link between the
_Dichopteris_ and _Thinnfeldia_ type of segment. Krasser gives a full
résumé of opinions expressed by other authors in regard to the position
of _Pachypteris_ (= _Dichopteris_) and decides in favour of a Cycadean
alliance.
[Illustration: FIG. 363. _Dichopteris visianica_, Zigno. (⅓ nat. size.
After Zigno.)]
A French Jurassic plant which Saporta[1475] made the type of a new
genus _Scleropteris_, and described as _S. Pomelii_, appears to be
indistinguishable from _Dichopteris_.
_Dichopteris_, though conveniently retained as a distinct genus, agrees
so closely, in the broad and forked rachis and in the fleshy pinnules,
with _Thinnfeldia_ that it would seem reasonable to regard the two
genera as members of the same group.
Several authors have drawn attention to the striking resemblance
in form and venation between the fronds of the Palaeozoic genus
_Odontopteris_ and those of _Ctenopteris_ and _Thinnfeldia_. In
_Odontopteris_, as in _Neuropteris_, another Palaeozoic genus, the
rachis occasionally bifurcates as in _Thinnfeldia_ and _Dichopteris_,
and the ultimate segments of some species of _Odontopteris_ (fig.
366, A) are practically identical with those of _Thinnfeldia_ and
_Ptilozamites_.
_Odontopteris_ is probably a Pteridosperm. There is no adequate reason
for supposing that this group of plants which played a prominent part
in the Permo-Carboniferous floras was no longer in existence during the
Mesozoic era.
Odontopteris.
Brongniart[1476] instituted the genus _Odontopteris_ for compound
fronds from the Coal-Measures characterised by pinnules attached by
the whole breadth of the base and traversed by numerous forked veins.
_Odontopteris_ is very rare in British Carboniferous rocks and “appears
to be restricted to the Middle and Upper Coal-Measures[1477].”
[Illustration: FIG. 364.
A. _Alethopteris lonchitica_ (Schloth.). ½ nat. size.
B. _Mariopteris muricata_ (Schloth.). × 2.
C. _Odontopteris_ cf. _alpina_ (Presl). ⅗ nat. size.
D. _O_. cf. _alpina_. Portion of pinna enlarged.
(A–D. From photographs by Dr Kidston.)]
Fronds large, bipinnate or tripinnate, the main rachis, which
may be dichotomously branched, bears long linear pinnae with
broadly linear or deltoid pinnules, acute or blunt, attached
by the whole of the base; the lower margin of the lamina,
which is usually entire and rarely lobed (e.g. _Odontopteris
osmundaeformis_)[1478], is often decurrent on the axis of the
pinna. The basal pinnule of each pinna is frequently attached by
a contracted base, and the lamina may differ in form from that of
the normal segments. Pinnules often occur on the main rachis,
and in some species the petiole bears modified pinnules which are
larger than the ultimate segments of the pinnae and in some cases
Cyclopteroid in shape. The pinnules are traversed by numerous
dichotomously branched veins; if a midrib is present it dies out in
the basal part of the lamina. In some species (genus _Mixoneura_)
pinnules of the Neuropteroid type, characterised by a well-defined
midrib, occur in association with typical Odontopteroid pinnules on
the same pinna.
[Illustration: FIG. 365. _Odontopteris minor_, Brongn. (Rather less
than ⅓ nat. size. After Zeiller.) [The pinnules are omitted in the
right-hand branch.]]
The species represented in fig. 364, C, D, from the Middle
Coal-Measures of Barnsley, Yorkshire, illustrates the form and venation
of the _Odontopteris_ type of pinnule. Another species, _O. Reichiana_
Gutb.[1479], is also recorded by Kidston from the Lower Coal-Measures
of Lancashire. Some unusually good specimens of the type-species of the
genus _Odontopteris minor_, Brongn., have been figured by Zeiller[1480]
from the Coal-Measures of Blanzy (fig. 365) which show the dichotomy
of the main axis and the occurrence of Aphlebiae on the petiole.
The late Dr Weiss[1481] divided _Odontopteris_ into two sections,
_Xenopteris_ and _Mixoneura_, the pinnules of the former having the
form shown in fig. 364, D; while in species of the latter sub-genus
some of the pinnules are identical in form and venation with those of
_Neuropteris_ except that they are attached by the whole breadth of
the base. Zeiller[1482] employs _Mixoneura_ as a generic designation.
In an American species _O. Wortheni_ Lesq.[1483] the pinnules bear
numerous hairs like those on some species of _Neuropteris_ (fig. 373,
p. 570). The large size of the fronds of _Odontopteris_ suggested
to Weiss[1484] that they were borne on the stems of tree-ferns, but
Grand’Eury’s[1485] examination of specimens in the Coal-beds of central
France led him to picture the plant as bearing a tuft of leaves on
a short subterranean stem. Renault and Zeiller[1486], on the other
hand, obtained evidence in the Commentry Coal-field of fronds borne on
elongated stems which grew on the ground and were supported by stronger
plants. Stur[1487] was the first to suggest that _Odontopteris_ should
be excluded from the ferns. Grand’Eury’s[1488] supposed fertile
pinnules of _Odontopteris_ do not afford any satisfactory evidence
of the sporangial nature of the small swellings which he figures at
the ends of the veins. This author pointed out several years ago
that the petioles of some species of _Odontopteris_ possess the
anatomical features of _Myeloxylon_, a type of leaf-stalk which is now
known to belong to Pteridosperms. In a recent paper Grand’Eury[1489]
records the association of _Odontopteris_ fronds with small seeds
(_Odontopterocarpus_), a discovery which leaves little or no doubt as
to the Pteridospermic nature of the genus. The fronds of _Odontopteris_
are very similar in habit to those of _Neuropteris_, another
Pteridospermic genus.
The similarity between some _Odontopteris_ and _Thinnfeldia_ leaves,
to which attention has already been called, is well illustrated by
_O. genuina_ Grand’Eury[1490], a pinnule of which is represented in
fig. 366, A. _Odontopteris_ is a fairly widespread genus in Upper
Carboniferous and Lower Permian rocks, and is recorded also from
Triassic strata: it is represented in the Coal-fields of North America
and in several parts of Europe[1491].
In some fronds included in _Odontopteris_ the pinnae are characterised
by a broad irregularly lobed lamina which also forms a winged border to
the rachis. Examples of this form are afforded by _Odontopteris Browni_
Sew.[1492] from the Burghersdorp Series (Triassic?) of Cape Colony, and
_O. Fischeri_ described by Brongniart[1493] from the Permian of Russia.
The Russian species would perhaps be more appropriately placed in the
genus _Callipteris_, as Weiss[1494] suggests; the absence of venation
in _O. Browni_ renders generic identification unsatisfactory.
[Illustration: FIG. 366.
A. _Odontopteris genuina_ (Grand’Eury). (× 2⅝. After Renault and
Zeiller.)
B. _Callipteridium gigas_ (Gutb.). (× 2⅝. After Zeiller.)
C. _Callipteris Pellati_ (Zeill.). (× 1¾. After Zeiller.)
D. _C. lyratifolia_ (Goepp.). (× 1¾. After Zeiller.)]
Callipteris.
Brongniart[1495] instituted this genus for certain species of supposed
ferns previously referred to the genera _Pecopteris_, _Alethopteris_,
and _Neuropteris_. _Callipteris_ is a characteristic Permian plant
which is almost certainly a Pteridosperm. Zeiller has pointed out
that such descriptions of fertile specimens as have been written are
unsatisfactory. A few years ago, however, Grand’Eury[1496] recorded the
occurrence of seeds in association with Callipteris fronds in the Autun
district, and in some cases they were found attached to the pinnae
and rachis. The seeds are ovoid or spherical (5–10 mm. broad) and
smaller than those of _Neuropteris_. The drawings of fertile segments
published by Weiss[1497] afford no indication of reproductive organs.
Potonié[1498] figures some pinnules of _Callipteris conferta_ in which
the thick lamina is covered with sinuous grooves probably made by some
insect larvae: as he suggests, similar markings may have been mistaken
for the remains of sori. The occurrence of _Callipteris_ fronds
recorded by Weber and Sterzel[1499] in association with _Medullosa_
stems in the Lower Permian of Saxony is in accordance with Grand’Eury’s
conclusion.
Fronds reaching 1 metre in length, bipinnate or tripinnate, main
rachis frequently exhibiting a combination of dichotomous and
pinnate branching. Pinnae linear, usually crowded, decurrent on the
rachis; the pinnules on the lower side of the pinnae are continued
on to the rachis. Pinnules of the Pecopteroid type, entire or
slightly lobed, or of the Sphenopteroid type and more or less
deeply dissected (fig. 366 C, D), the lamina of adjacent pinnules
concrescent; on the lower pinnae the lamina may be continuous as in
an Alethopteris pinnule. A midrib may extend almost to the bluntly
rounded apex of the ultimate segments, giving off oblique, simple,
or forked veins, the lowest of which arise directly from the
rachis; in the Sphenopteroid forms the lateral veins are given off
at a more acute angle.
A striking feature of the genus is the occurrence of pinnules on the
main rachis, as in _Odontopteris_. Zeiller has wisely extended the
application of _Callipteris_ to fronds possessing this character
irrespective of the entire or lobed form of the ultimate segments.
He found among the numerous examples of the genus obtained from
Autun[1500] and Lodève[1501] transitional forms connecting such
species as _C. conferta_ (fig. 367) and _C. Pellati_ Zeill. (fig. 366,
C) in which the Pecopteroid pinnules are slightly lobed, with _C.
lyratifolia_ (Goepp.) (fig. 366, D), _C. flabellifera_[1502] (Weiss),
and _C. Bergeroni_ Zeill. characterised by deeply lobed Sphenopteroid
segments.
_Callipteris conferta_ (Sternberg)[1503]. Fig. 367.
1723. Scheuchzer, Herb. Diluv. Pl. II., fig. 3.
1826. _Neuropteris conferta_, Sternberg, Flor. Vorwelt, p. 17.
1849. _Callipteris conferta_, Brongniart, Tableau, p. 24.
This polymorphic species (fig. 367) is one of the most characteristic
Permian plants. The oval-linear pinnules, attached by the whole base,
occur on both pinnae and rachis; this feature, the thick texture of the
lamina, and the linear, obliquely set, pinnae render the fronds easily
recognisable. The fronds bore seeds.
[Illustration: FIG. 367. _Callipteris conferta_. From the Permian of
Aschbach, Rhenish Prussia (British Museum, No. 39052).]
In a recent account of some Permian plants from Germany, Schuster[1504]
refers a portion of a frond to _Callipteris conferta_ (Sternberg) var.
_polymorpha_ Sterzel, which is characterised by unusually large and
polymorphic pinnules. In size and shape the pinnules recall those of
_Neuropteridium validum_ Feist.
Callipteridium.
The name _Callipteridium_, created by Weiss[1505] as a sub-genus of
_Odontopteris_, is applied by Zeiller and other authors to a few Upper
Carboniferous and Permian species characterised by the occurrence
of simply pinnate pinnae on the main rachis between the bipinnate
primary pinnae. Single pinnules are borne directly on the rachis of the
primary pinnae between the pinnate branches. The form and venation of a
typical pinnule are shown in fig. 366, B. _Callipteridium pteridium_,
originally recorded by Schlotheim as _Filicites pteridius_[1506],
has been fully described by Renault and Zeiller from unusually large
specimens found in the Commentry Coal-field[1507]. This species
illustrates the peculiar morphological features of the genus. The
main rachis of the tripinnate fronds, several metres long, shows a
combination of dichotomous and pinnate branching; from the zigzag
and forked axis are given off bipinnate pinnae and, between these,
shorter pinnate branches. The pinnules closely resemble those of
_Callipteris conferta_ but reach a greater length; the pinnules borne
on the rachises of the lateral branches differ from the others in their
broader base and more triangular lamina.
No fertile specimens have been found. It is probable that
_Callipteridium_ was not a true fern, and that White[1508] is correct
in including it among the Pteridosperms.
Archaeopteris.
In 1852 Forbes[1509] published a brief description of some supposed
fern fronds, found by the Geological Surveyors of Ireland in Upper
Devonian rocks of Kilkenny, under the name _Cyclopteris hibernica_.
The Irish specimens were more fully described by Baily[1510] in
1858. Fronds of the same type were referred by other authors to
_Cyclopteris_, _Adiantites_ or _Noeggerathia_, until Schimper[1511]
proposed the generic name _Palaeopteris_ on the ground that the fronds
described by Forbes and Baily are distinguished by the nature of
their fertile pinnae from the sterile leaves included in Brongniart’s
provisional genus _Cyclopteris_. The earlier use of _Palaeopteris_ by
Geinitz for an entirely different plant led Dawson[1512] to institute
the genus _Archaeopteris_. The genus _Archaeopteris_ may be defined as
follows:
Fronds bipinnate, reaching a considerable length (90 cm.); the
stout rachis bears long linear pinnae; sterile pinnules obovate
or cuneate with an entire, lobed, fimbriate, or laciniate lamina
traversed by divergent dichotomously branched veins. The fertile
pinnae usually occur on the lower part of the rachis; pinnules with
a much reduced lamina bear numerous fusiform or oval exannulate
sporangia (fig. 369, A, E, H), sessile or shortly stalked,
singly, or in groups of two or three. The base of the petiole is
characterised by a pair of partially adnate stipules (fig. 369,
C, D), and single pinnules or scales occur in some species on the
rachis between the pinnae and on the petiole.
[Illustration: FIG. 368. _Archaeopteris hibernica_. (From a specimen in
the Science and Art Museum, Dublin. Rather less than ⅙ nat. size.)]
_Archaeopteris hibernica_ (Forbes). Figs. 368, 369, A–C.
The specimen from Kilkenny represented in fig. 368 has a length of
over 80 cm. The upper pinnae bear numerous imbricate obovate pinnules
(fig. 369, A, B) with an entire or very slightly fimbriate margin,
while on the shorter lower pinnae the ultimate segments are reduced to
a slender axis bearing numerous fusiform sporangia, 2–3 mm. in length.
Kidston[1513] has pointed out that sporangia occasionally occur on the
edge of ordinary pinnules, and he first recognised the stipular nature
of the scale-like appendages which Baily noticed on the swollen petiole
base (5 cm. broad) of the Irish species (fig. 369, C). Restorations
of _Archaeopteris hibernica_ have been figured by Baily[1514] and
by Carruthers[1515], but the description of the fertile pinnae by
the latter author requires modification in the light of Kidston’s
description of the Dublin specimens.
• • • • •
_Archaeopteris_ is recorded from Upper Devonian rocks of the South of
Ireland, Belgium, Germany, Southern Russia, Bear Island, and Ellesmere
Land in the Arctic regions, Canada, Pennsylvania, and elsewhere.
Many of the specimens described under different names bear a close
resemblance, which in some cases probably amounts to specific identity,
to _A. hibernica_. _A. Jacksoni_ originally described by Dawson[1516]
and more recently by Smith and White[1517] from Devonian rocks of
Maine, the Canadian type _A. gaspiensis_ Daws., and some species
figured by Lesquereux[1518] from Pennsylvania, are examples of forms
which present a striking similarity in habit to the Irish species. The
Belgian Devonian fossils named by Crépin[1519] _Palaeopteris hibernica_
var. _minor_ are regarded by him as probably identical with Goeppert’s
species _Cyclopteris Roemeriana_ from the neighbourhood of Aachen. Heer
recorded _Archaeopteris Roemeriana_ from Upper Devonian beds in Bear
Island, and Nathorst[1520], who has published a more complete account
of the Arctic forms, draws attention to the resemblance of some of
them to _A. hibernica_. A species described by Schmalhausen[1521] from
the Upper Devonian of Southern Russia as _A. archetypus_ (fig. 369,
D) appears to differ from _A. hibernica_ in the slightly less reduced
lamina of the fertile segments. This species has been more adequately
illustrated by Nathorst[1522] from material collected in Ellesmere
Land: he is unable to confirm Schmalhausen’s statement that the pinnae
are spirally disposed.
The species _A. fimbriata_ (fig. 369, G) described by Nathorst from
Bear Island is characterised by the more deeply dissected lamina of the
sterile pinnules. In _A. fissilis_ Schmal. from Russia and Ellesmere
Land the lamina (fig. 369, E, F) is cut up into filiform segments: a
fertile pinnule of this species is represented in fig. 369, E.
Some sterile impressions figured by Krasser[1523] from Palaeozoic
strata (Lower Carboniferous or Upper Devonian?) in the province of
Nanshan in China as _Noeggerathia acuminifissa_ are considered by
Zeiller[1524] to be portions of an _Archaeopteris_ or _Rhacopteris_
frond. The resemblance to the former genus is however by no means close
enough to warrant a reference to _Archaeopteris_. The sterile specimens
described by Stur[1525] from the Culm of Altendorf as species of
_Archaeopteris_ are probably not generically identical with the Irish
and Arctic species. The dichotomous branching of the rachis in _A.
Tschermaki_ and _A. Dawsoni_ is a feature unknown in _Archaeopteris_.
In the absence of fertile pinnae the separation of _Archaeopteris_ from
_Rhacopteris_ is by no means easy.
[Illustration: FIG. 369.
A. _Archaeopteris hibernica._ Fertile pinna. Dublin Geological
Survey Museum. (Reduced. After Kidston.)
B. _A. hibernica._ Pinnule. (Slightly enlarged. After Carruthers.)
C. _A. hibernica._ Base of petiole. (Dublin Museum. After Kidston.)
D. _A. archetypus._ Base of petiole: Ellesmere Land. (After
Nathorst. ⅚ nat. size.)
E. _A. fissilis._ Sporangia. (Slightly enlarged. After
Schmalhausen.)
F. _A. fissilis._ Sterile pinnule. Ellesmere Land. (Slightly
enlarged. After Nathorst.)
G. _A. fimbriata._ Bear Island. (After Nathorst. ⅚ nat. size.)
H. _Archaeopteris sp._ Ellesmere Land. (After Nathorst. ⅚ nat.
size.)]
_Archaeopteris_ was regarded by Carruthers as a fern closely allied
to recent species of Hymenophyllaceae, but this conclusion was based
upon an interpretation of the fertile segments which Kidston[1526]
has shown to be incorrect. The latter author regarded the presence of
stipules and the structure of the exannulate sporangia as evidence of
a Marattiaceous alliance. In a later reference to _Archaeopteris_,
Kidston expresses the opinion that the genus is not a true fern but
a member of the Cycadofilices or Pteridosperms, a view shared by
Grand’Eury[1527] and doubtless by many other palaeobotanists. The
sporangia of _Archaeopteris_ appear to be of the same type as those
of _Dactylotheca_ (fig. 290, E, p. 399). Schmalhausen gave expression
to his disagreement with Nathorst and other authors who referred
_Archaeopteris_ to the Marattiaceae by proposing the distinctive
group-name Archaeopterideae.
There can be little doubt that the reproductive organs of
_Archaeopteris_ so far discovered are microsporangia, and that the
plant bore seeds. The sporangia are larger than those of any known fern
and, as Kidston points out, they are similar to those of _Crossotheca_
which he has shown to be microsporangia of the Pteridosperm
_Lyginodendron_. The presence of stipules in _Archaeopteris hibernica_,
_A. fimbriata_, _A. archetypus_ (fig. 369, D) and probably throughout
the genus does not materially affect the question of taxonomic
position. Stipules are a characteristic feature of Marattiaceae and,
in a reduced form, of Osmundaceae, but similar appendages are borne at
the base of the petiole of the Cycad _Ceratozamia_. The occurrence of
Aphlebiae on the rachis of _Archaeopteris_ is a feature shared by the
fronds of _Neuropteris_ and other Pteridosperms.
Neuropteris.
The fronds for which Brongniart[1528] created this genus, though
suspected by Stur in 1883 as wrongly classed among the ferns, have only
recently been shown to be the leaves of Pteridosperms. As yet only one
case is recorded in which
_Neuropteris_ pinnae occur in organic connexion with seeds[1529],
but it is almost certain that the genus as a whole must be placed in
this generalised group. Renault[1530] pointed out that the petioles
of Neuropteris fronds from Autun had the anatomical features of
_Myeloxylon_ (petiole of _Medullosa_). Since Kidston’s important
discovery of seed-bearing pinnae of _N. heterophylla_, Grand’Eury[1531]
has recorded the association of Neuropteris fronds with seeds in
French Coal-fields. By some of the older authors _Neuropteris_ was
compared with _Osmunda_ because of a similarity in venation. In the
frequent dichotomy of the frond and in the occurrence of pinnules on
the rachis, _Neuropteris_ closely resembles _Odontopteris_[1532]: there
can be little doubt as to the close relationship of the Pteridosperms
possessing these two types of foliage. _Neuropteris_ may be defined as
follows:
Fronds reaching a considerable size, probably in soma cases a
length of 10 metres[1533]; bi- or tri-pinnate; the rachis may be
dichotomously branched (figs. 354, D; 370); both rachis and petiole
bear single pinnules, those on the latter frequently differ from
the normal leaflets in their larger Cyclopteroid laminae (fig.
370). Pinnules entire, rarely slightly lobed, broadly linear,
attached by a small portion of the base, which is usually more or
less cordate. In _N. Grangeri_ Brongn. the pinnules are attached by
a short pedicel[1534]. The midrib always dies out before reaching
the blunt or pointed apex of the lamina and gives off at an acute
angle numerous secondary veins characterised by their arched course
and repeated forking.
[Illustration: FIG. 370. _Neuropteris_ frond with _Cyclopteris_
leaflets. English Coal-Measures. (From a block given to me by Mr
Carruthers. A.C.S.)]
Potonié describes the secondary veins of the pinnules of _Neuropteris
pseudogigantea_[1535] as occasionally anastomosing, a feature which may
be regarded as a step towards the reticulate venation of the closely
allied genus _Linopteris_.
Renault[1536] described some petrified pinnules of _Neuropteris_ in
which the mesophyll shows a differentiation into upper palisade tissue
and lacunar tissue below; the lower epidermis is infolded at intervals
where grooves (probably stomatal) occur like those on the leaves of an
Oleander (_Nerium oleander_).
The rachises of Neuropteris fronds are described by Grand’Eury under
the generic name _Aulacopteris_[1537].
_Neuropteris heterophylla_, Brongniart[1538]. Figs. 354, E; 371.
This species is characteristic of the Lower Coal-Measures of Britain;
it occurs also in the Middle Coal-Measures and is a common type in
Upper Carboniferous rocks in various parts of the world. The fronds are
large and tripinnate, the rachis is often dichotomously branched and
Cyclopteroid pinnules may occur on the petiole. The pinnules, 5–20 mm.
in length and 3–8 mm. broad, have a rounded apex (fig. 354, E, p. 535).
[Illustration: FIG. 371. _Neuropteris heterophylla._ From a specimen in
the Manchester Museum. ½ nat. size. M.S.]
As shown in fig. 371 which represents a primary pinna, the small
pinnules on the lower branches are gradually replaced in the upper
portion of the specimen by falcate segments.
_Neuropteris macrophylla_, Brongniart[1539]. Figs. 354, D, D′; 372.
The rachis of the large fronds of this species illustrates the
dichotomous habit of many Neuropteris fronds, also the occurrence on
the petiole of large Cyclopteroid pinnules (cf. fig. 370). The small
piece of a pinna reproduced in fig. 372 shows the slender attachment
of the segments, the blunt apex, and the Neuropteroid venation. Single
pinnules of this species may be distinguished from those of _N.
Scheuchzeri_ by the blunter apex, the absence of the pair of small
Cyclopteroid pinnules on the same branch and by the absence of hairs.
_N. macrophylla_ is characteristic of the Upper Coal-Measures of
Britain.
[Illustration: FIG. 372. _Neuropteris macrophylla_, Brongn. From a
photograph by Mr Hemingway.]
_Neuropteris Scheuchzeri_, Hoffmann. Figs. 354, F; 373.
Fragments of this well-known Coal-Measure species were figured by
Scheuchzer in his _Herbarium Diluvianum_[1540] as _Lithosmunda minor_,
and by Lhywd (Luidius[1541]) as _Phyllites mineralis_ as early as
1760. _Neuropteris Scheuchzeri_, so named by Hoffmann in 1826, is
a type which many authors have described under different names.
Lesquereux[1542] figured it as _N. hirsuta_ from the Coal-fields of
Pennsylvania, and under the same name it is recorded by Fontaine and
White[1543] from Permian rocks of Virginia. The oval patches on the
surface of a pinnule described by these authors as sori are certainly
not of that nature. The same species is described by Bunbury[1544] from
Nova Scotia as _N. cordata_ Brongn. var. _angustifolia_. For a full
synonymy of the species reference should be made to lists published by
Kidston[1545], White[1546], and Zeiller[1547].
[Illustration: FIG. 373. _Neuropteris Scheuchzeri._ From a specimen (v.
2009) in the British Museum. ¾ nat. size.]
The large tripinnate fronds are characterised by the long linear-
or oval-lanceolate pinnules (fig. 373)[1548] with a pointed apex
and numerous bristle-like hairs on the lamina; two much smaller
Cyclopteroid segments occur at the base of the pinnae which are
terminated by the linear leaflets (fig. 354, F, p. 535).
_Neuropteris Scheuchzeri_ is characteristic of the Upper and Middle
Coal-Measures of Britain and is recorded from several localities in
North America and the Continent. Zalessky[1549] has recently recorded
the species from the Coal-Measures of Donetz. The frequent occurrence
of detached pinnules points to a caducous habit. Even single leaflets
can, however, be identified by their large size, the pointed apex, and
hairy lamina. The hairs are preserved as fine oblique lines simulating
veins; they were so described by Roemer[1550] who took them for
cross-connexions between the secondary veins and referred the pinnules
to Gutbier’s genus _Dictyopteris_.
Another example of _Neuropteris_ with hairy pinnules is described from
the Commentry Coal-field by Renault and Zeiller as _N. horrida_[1551].
The oval-linear, bluntly rounded, pinnules are characterised by a
median band of hairs on each surface and a narrower strip at the edge
of the lamina.
Cyclopteris.
This generic name was created by Brongniart in 1828[1552] for specimens
which he believed to be complete single leaves of orbicular or reniform
shape similar to those of _Trichomanes reniforme_. The lamina is
traversed by numerous dichotomously branched veins which spread from
the centre of the base.
It was suspected by Lindley and Hutton[1553] that certain Cyclopteris
leaves belonged to the frond of a species of _Neuropteris_, and some
years later Lesquereux[1554] concluded that Brongniart’s genus was
founded on orbicular leaflets of _Neuropteris_. In 1869 Roehl[1555]
figured a specimen of _Neuropteris_ bearing Cyclopteroid pinnules on
its rachis. It is now universally admitted that _Cyclopteris_ is not a
distinct genus and that the specimens so named were borne as modified
pinnules on the main rachis of _Neuropteris_ and _Odontopteris_. It
is, however, convenient to retain the name for detached leaflets which
cannot be referred to the fronds on which they were borne. A specimen
found by Mr Hemingway in the Upper Coal-Measures of Yorkshire and
described in 1888[1556] affords a striking example of the large size
attained by what was probably a frond of _Neuropteris_. The piece of
main rachis reached a length of over 120 cm. and bore five pairs of
Cyclopteris pinnules, some of which were 7 cm. long and 5 cm. broad.
The complete frond must have reached a length of at least 4 metres.
Fig. 370 shows some typical Cyclopteroid leaflets on the petiole of a
_Neuropteris_ frond.
Linopteris.
The Upper Palaeozoic fronds included in this genus are more familiar
as species of _Dictyopteris_. Potonié[1557] has, however, pointed out
that the creation of this name by Lamouroux in 1809 for a genus of
Brown Algae which is still retained, makes it advisable to fall back
upon the designation _Linopteris_. Gutbier[1558] proposed the genus
_Dictyopteris_ in 1835: _Linopteris_ was first used by Presl[1559] in
1838. The fronds so named are identical with species of _Neuropteris_
except in the anastomosis of the secondary veins; _Linopteris_
bears to _Neuropteris_ the same relation as _Lonchopteris_ bears to
_Alethopteris_. As in _Neuropteris_, Cyclopteroid pinnules occur on
the petioles of _Linopteris_, but the veins form a fine reticulum.
Grand’Eury[1560] records the association of _Linopteris Brongniarti_
with seeds belonging to the genus _Hexagonocarpon_, a fact which points
to the Pteridosperm nature of the foliage.
Some fertile pinnules of _Linopteris Schutzei_ (Roemer) are described
by Zeiller[1561] from Autun as bearing on the under surface of the
lamina two rows of long and pointed sporangia, probably united in
groups. The presumption is that these are microsporangia.
Fig. 374 is a reproduction of a careful drawing, originally published
by Zeiller[1562], of a pinnule of the type-specimen of Gutbier’s
species _Linopteris neuropteroides_. This species differs from
_Linopteris obliqua_, instituted by Bunbury[1563] for specimens
obtained by Lyell[1564] from the Coal-Measures of Nova Scotia, in
the smaller size of the meshes. _Linopteris obliqua_ occurs in the
Upper and Middle Coal-Measures of Britain; it is recorded by Zeiller
from Asia Minor, by Lesquereux[1565] from Pennsylvania, and by other
authors from several European localities. The pinnules frequently occur
detached from the frond and like those of some species of _Neuropteris_
were caducous. _Linopteris_ is rare in British strata.
[Illustration: FIG. 374. _Linopteris neuropteroides_, Gutb. (Pinnule of
type-specimen. Enlarged. After Zeiller.)]
Alethopteris.
The name _Alethopteris_, instituted by Sternberg[1566], is applied to
compound fronds often reaching a considerable size, exhibiting the
following features:
The linear pinnules are attached by the whole breadth of the base,
with the lower edge of the lamina decurrent and usually continuous
with that of the next pinnule (figs. 290, A, p. 399; 375). The
ultimate segments are entire, with an acute or rounded apex and
often characterised by a fairly thick lamina convex on the upper
surface. From a prominent midrib, continued to the apex of the
pinnule, numerous simple and forked secondary veins are given
off at a wide angle, the decurrent portion of the lamina being
supplied by veins direct from the axis of the pinna. In the upper
part of a frond or primary pinna the pinnules may be replaced by
a continuous, lobed, or entire simple lamina. The main rachis
occasionally exhibits dichotomous branching, but the fronds are for
the most part constructed on the pinnate plan. Single Cyclopteroid
pinnules[1567] occur on the petiole of some species of the genus.
In certain species of _Alethopteris_ the pinnules appear to have been
deciduous as in _Didymochlaena_ among recent ferns[1568]. A piece of
cuticle from the upper surface of a pinnule of _Alethopteris Grandini_
(Brongn.) figured by Zeiller[1569] shows very clearly the polygonal
form and straight walls of most of the epidermal cells, those above the
veins being almost rectangular. The position of the sunken stomata is
revealed by small circular spaces surrounded by a circle of cells.
The absence of fertile specimens of this common genus of Upper
Carboniferous plants led Stur[1570] to exclude it from the ferns.
Although no seeds have so far been found in organic connexion with an
Alethopteris frond, it is certain that some species, probably all,
represent the foliage of Pteridosperms. Renault was the first to
describe petrified specimens of _Alethopteris_ fronds exhibiting the
anatomical structure of _Myeloxylon_ (leaf-axis of _Medullosa_). The
calcareous nodules from English Coal-seams contain numerous fragments
of the Myeloxylon type of rachis bearing Alethopteroid pinnules.
The constant association of the fronds of _Alethopteris lonchitica_
and _Trigonocarpon_ seeds noticed by Mr Hemingway in the Coal-Measures
of Yorkshire led him to regard the species as seed-bearing: it has
since been recognised as the foliage of the Pteridosperm _Medullosa
anglica_[1571].
Grand’Eury[1572] has recorded the association in French Coal-fields of
species of _Alethopteris_ with _Trigonocarpon_ and _Pachytesta_ seeds.
_Alethopteris lonchitica_ (Schlotheim)[1573]. Figs. 364, A; 290, A.
This species, described by Schlotheim in 1820 as _Filicites
lonchiticus_ and previously figured by Scheuchzer[1574], is abundant
in the Middle and Lower Coal-Measures of Britain[1575]. It is
characterised by large tripinnate fronds, probably quadripinnate in the
lower part, bearing primary pinnae of a more or less triangular form
divided into pinnate branches replaced in the apical region by linear
segments. The pinnules, 8–30 mm. long and 3–5 broad, are linear- or
oval-lanceolate with an obtuse apex; the upper margin of the lamina is
slightly contracted at the base, while the lower edge is decurrent.
[Illustration: FIG. 375. _Alethopteris Serlii_ (Brongn.). From a
specimen in the York Museum. ¾ nat. size.]
_Alethopteris Serlii_ (Brongniart)[1576]. Fig. 375.
This species, figured by Parkinson in 1811, closely resembles _A.
lonchitica_, but is distinguished by the more crowded and relatively
longer pinnules which are joined to one another by a narrow connecting
lamina (Fig. 375). The secondary veins in _A. Serlii_ are rather finer
and more numerous. Grand’Eury[1577] records the association of the seed
_Pachytesta_ with fronds of this species in the Coal-Measures of St
Étienne.
_A. Serlii_ is very abundant in the Upper Coal-Measures but rare in
the Middle Coal-Measures of Britain[1578].
Lonchopteris.
This name was proposed by Brongniart[1579] for sterile fronds from
Upper Carboniferous rocks which are practically identical with
species of _Alethopteris_, but differ in the reticulate venation of
the pinnules. It has been pointed out in a previous chapter[1580]
that _Lonchopteris_ is usually used for Palaeozoic species, the
Wealden leaves, which were placed in this genus by Brongniart, being
transferred to _Weichselia_.
There can be little doubt as to the close relationship of
_Lonchopteris_ with _Alethopteris_: both may be referred to the
Pteridosperms. _Lonchopteris rugosa_ Brongn.[1581] (fig. 290, B, p.
399) and _L. Bricei_ Brongn., both British species, are fairly common
in Upper Carboniferous strata. In _L. rugosa_, a Middle Coal-Measures
species, the anastomosing secondary veins form polygonal meshes (fig.
290, B, p. 399) smaller than those of _L. Bricei_.
Pecopteris.
Reference has already been made to this genus in the chapter on
Marattiales, so far as regards certain species of fertile fronds the
sporangia of which resemble those of recent Marattiaceae. It is,
however, by no means safe to assume that such Pecopteris fronds were
borne on stems having the anatomical characters of ferns. The sporangia
in some at least of the species may have contained microspores. In
one Upper Carboniferous species usually referred to Pecopteris, _P.
Pluckeneti_, Schlot., Grand’Eury[1582] has recorded the occurrence of
seeds on the pinnules of the ordinary fronds. This species will be
referred to in Volume III. The substitution of such generic names as
_Ptychocarpus_, _Asterotheca_, _Hawlea_, _Dactylotheca_ and others
for the purely provisional designation _Pecopteris_ indicates a step
towards a conclusion as to natural affinity. The probability is that
_Pecopteris_, as applied to Palaeozoic species, in many cases stands
for the compound fronds of true ferns, but the possibility of the
inclusion of those of Pteridosperms in the same category is by no means
excluded. The designation _Pecopteris_ may conveniently be retained for
sterile bipinnate, tripinnate, or quadripinnate fronds bearing pinnules
having the following characteristics:
Lamina short, attached to the rachis by the whole of the base and
at a wide angle, with the edges parallel or slightly converging
towards the usually blunt apex; adjacent pinnules may be continuous
basally by a narrow lamina. A well-marked midrib extends to the
apex and gives off simple or forked lateral veins almost at right
angles (fig. 352, D, p. 529).
Hydathodes like those on the leaflets of _Polypodium vulgare_ and
other recent ferns[1583] are occasionally seen at the ends of the
lateral veins of Pecopteris pinnules.
In addition to the examples of Palaeozoic fronds with the _Pecopteris_
form of pinnule referred to in chapter XXII., the species _Pecopteris
arborescens_ may be briefly described.
_Pecopteris arborescens_ (Schlotheim)[1584]. Figs. 352, D: 376.
The species named by Schlotheim _Filicites arborescens_ in 1804 is
characteristic of the Upper Coal-Measures and is recorded also from
Permian strata[1585].
Fronds large; the rachis, which may reach a breadth of 3 cm.[1586],
gives off long ovoid-lanceolate pinnae in two alternate rows
(fig. 376); pinnules small, 1·5–4mm. long and 1–2mm. broad,
contiguous, with rounded apex, attached approximately at right
angles; the upper surface of the lamina is slightly convex and may
be hairy[1587]. The fertile pinnules, identical in shape with the
sterile, bear groups of ovoid exannulate sporangia (synangia). The
midrib extends to the apex of the pinnule and gives off simple
veins at a wide angle (fig. 352, D).
Our knowledge of the reproductive organs is very meagre. Grand’Eury
described the synangia as consisting of 3–5 sporangia borne on a
central receptacle; sporangia have been described also by Stur[1588],
Renault and Zeiller[1589], and Potonié[1590], but no fertile British
specimens are recorded. Stur places this species in the genus
_Scolecopteris_, and Potonié regards the sporangia found by him on
Permian fronds, which may be identical with _Pecopteris arborescens_,
as conforming to those of the _Asterotheca_ type. It is impossible to
decide on the evidence available whether this species is a Pteridosperm
or a fern, but there is a natural inclination in doubtful cases to give
preference to the first of these two choices.
[Illustration: FIG. 376. _Pecopteris arborescens_ (Schloth.). From
the Upper Coal-Measures of Radstock. From a photograph by Dr
Kidston. Reduced.]
The numerous fronds from Carboniferous and Permian rocks described
as species of _Pecopteris_ exhibit a considerable range of variation
in the form of the pinnules. In many species the pinnules are of the
type represented in fig. 352, D; in others the lamina of the ultimate
segments is slightly contracted at the base and the secondary veins
are given off at a more acute angle, as in _Pecopteris polymorpha_,
Brongn.[1591] In _Pecopteris unita_, Brongn., already described as
_Ptychocarpus unita_[1592], the pinnules are joined together except
in the apical region. Some fronds included in _Pecopteris_ possess
pinnules in which Pecopteroid and Sphenopteroid features are combined;
_P. Sterzeli_, Zeill.[1593] and _P. Pluckeneti_, Schlot. are examples
of fronds in which the pinnules are lobed as in _Sphenopteris_, but the
base of the lamina is only slightly contracted and the venation is not
that of typical Sphenopteris species.
The species to which Potonié has applied the generic name
_Alloiopteris_[1594] also illustrates the impossibility of drawing a
sharp line between _Pecopteris_ and _Sphenopteris_. The fronds already
described in chapter XXV. under the designation _Corynepteris_ bear
pinnules with a contracted base; in some species the lamina is lobed,
but in others (fig. 354, G) it is entire with a midrib nearer one edge
than the other. The species which Potonié assigns to _Alloiopteris_,
like many other Sphenopteroid and Pecopteroid fronds, are characterised
by the occurrence of an abnormal pinnule (aphlebia) at the base of
each pinna (fig. 354, G, p. 535). Young fronds of _Pecopteris_ are
occasionally met with showing very clearly the circinate vernation of
the pinnae as in the leaves of _Cycas_ and _Angiopteris_ represented in
fig. 220, p. 283. The genus _Spiropteris_ was created by Schimper[1595]
for coiled unexpanded fronds of fossil ferns; it is however superfluous
to apply a distinctive term to specimens of this kind.
The designation _Pecopteris_ is employed chiefly for leaves of
Palaeozoic age which are unknown in the fertile state, or do not afford
sufficient evidence as to the nature of the sporangia to justify the
substitution of a special generic name. Many Mesozoic species have also
been referred to _Pecopteris_, but most of these are more appropriately
included in Brongniart’s later genus _Cladophlebis_. The pinnules of
_Cladophlebis_, as Brongniart pointed out, are intermediate between
_Pecopteris_ and _Neuropteris_; they are usually attached by the whole
breadth of the base, as in _Pecopteris_, but the more acute origin,
more arched form, and more frequent dichotomy of the lateral veins
are features shared by _Neuropteris_. As a rule, Mesozoic sterile
fronds with straight or folded, entire or dentate pinnules are of the
Cladophlebis type: this genus is especially characteristic of Rhaetic
and Jurassic floras. Examples of _Cladophlebis_ pinnules are shown in
figs. 256, 257 (pp. 340, 342). It is to be regretted that authors do
not make more use of the generic name _Cladophlebis_ in describing
sterile fronds, instead of following the misleading and unscientific
practice of employing such genera as _Pteris_, _Asplenites_, and others
on wholly insufficient grounds.
LIST OF WORKS REFERRED TO IN THE TEXT.
=Amalitzky, W.= (01) Sur la découverte, dans les dépôts permiens
supérieurs du Nord de la Russie, d’une flore Glossoptérienne
&c. _Compt. Rend._ vol. CXXXII. p. 591.
=Arber, E. A. N.= (02) On the distribution of the Glossopteris Flora.
_Geol. Mag._ vol. IX. p. 346.
—— (02²) The Clarke collection of fossil plants from New South
Wales. _Quart. Journ. Geol. Soc._ vol. LVIII. p. 1.
—— (03) Notes on some fossil plants collected by Mr Molyneux in
Rhodesia. _Quart. Journ. Geol. Soc._ vol. LIX. p. 288.
—— (05) Catalogue of the fossil plants of the Glossopteris Flora
in the British Museum. A monograph of the Permo-Carboniferous
Flora of India and the Southern Hemisphere. _London._
—— (05²) The Sporangium-like organs of _Glossopteris Browniana_,
Brongn. _Quart. Journ. Geol. Soc._ vol. LXI. p. 324
—— (05³) The fossil flora of the Culm-measures of N. W. Devon &c.
_Phil. Trans. R. Soc._ vol. CXCVII. p. 291.
—— (06) On the past history of Ferns. _Annals Bot._ vol. XX. p.
215.
=Arber, E. A. N.= and =H. H. Thomas.= (08) On the structure of
_Sigillaria scutellata_, Brongn. and other Eusigillarian stems,
in comparison with those of other Palaeozoic Lycopods. _Phil.
Trans. R. Soc._ vol. CC. p. 133.
=Armour, H. M.= (07) On the Sorus of Dipteris. _New Phytologist_,
vol. VI. p. 238.
=Atkinson, G. F.= (94) The study of the biology of Ferns, by the
collodion method. _New York._
=Auerbach, J.= and =H. Trautschold.= (60) Ueber die Kohlen von
Central Russland. _Nouv. Mém., Soc. Imp. Naturalistes Moscou_,
vol. XIII.
=Bäsecke, P.= (08) Beiträge zur Kenntnis der physiologischen Scheiden
der Achsen und Wedel der Filicinen &c. _Bot. Zeit._ Heft
II.–IV. Abt. I.
=Baily, W. H.= (59) On the fructification of _Cyclopteris hibernica_
(Forbes), from the Upper Devonian or Lower Carboniferous strata
at Kiltorkan Hill, County Kilkenny. _Brit. Assoc. Rep. London_,
1859, p. 75. (_Leeds meeting_, 1858.)
—— (60) On _Corynepteris_, a new generic form of fossil fern.
_Journ. Geol. Soc. Dublin_, vol. VIII. p. 237.
—— (75) Figures of characteristic British fossils. _London._
=Baker, J. G.= (67) Descriptions of six new species of simple fronded
Hymenophyllaceae. _Journ. Linn. Soc._ vol. IX. p. 335.
—— (68) On the geographical distribution of Ferns. _Trans. Linn.
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=Buckman, J.= (45) See Murchison, R. I.
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solenostelic ferns. _Annals Bot._ vol. XIV. p. 71.
—— (03) Observations &c. _Ibid._ vol. XVII. p. 689.
—— (05) On the anatomy of _Archangiopteris Henryi_ and other
Marattiaceae. _Annals Bot._ vol. XIX. p. 259.
—— (07–09) See Kidston, R. and D. T. Gwynne-Vaughan.
—— (08) On the real nature of the Tracheae in the ferns.
_Annals Bot._ vol. XXII. p. 517.
—— and =R. Kidston=. (08) On the origin of the adaxially curved
leaf-trace in the Filicales. _Proc. R. Soc. Edinb._ vol.
XXVIII. pt. vi. p. 433.
=Hall, Kate M.= (91) See Jennings, A. Vaughan, and Kate M. Hall.
=Halle, T. G.= (07) Einige krautartige Lycopodiaceen Paläozoischen
und Mesozoischen Alters. _Arkiv Bot._ Bd. VII. No. 5.
=Hannig, E.= (98) Ueber die Staubgrübchen auf den Stämmen und
Blattstielen der Cyathaeaceen und Marattiaceen. _Bot. Zeit._ p.
9.
=Harvey-Gibson, R. J.= (94) Contributions towards a knowledge of the
anatomy of the genus _Selaginella_, Spr. _Annals Bot._ vol.
VIII. p. 133.
—— (96) Contributions &c. _Ibid._ vol. X. p. 77.
—— (97) Contributions &c. _Ibid._ vol. XI. p. 123.
—— (02) Contributions &c. _Ibid._ vol. XVI. p. 449.
=Haughton, S.= (59) On _Cyclostigma_, a new genus of fossil plants
from the Old Red Sandstone of Kiltorkan, W. Kilkenny. _Journ.
Roy. Dublin Soc._ vol. II. p. 407.
=Hawkshaw, J.= (42) Description of the fossil trees found in the
excavations for the Manchester and Bolton railway. _Trans.
Geol. Soc._ [2] vol. VI. p. 173.
=Hayden, H. H.= (07) The stratigraphical position of the
Gangamopteris beds of Kashmir. _Rec. Geol. Surv. India_, vol.
XXXVI. pt. i.
=Heer, O.= (71) Fossile Flora der Bären Inseln. _Flor. Foss. Arct._
vol. II.
—— (74) Die Kreideflora der Arctischen Zone. _K. Svensk.
Vetenskaps-Akad. Hand._ Bd. XII. [_Flor. Foss. Arct._ vol. III.
1875.]
—— (75) _Flora Fossilis Arctica_, vol. III.
—— (76) Jura-Flora Ostsibiriens und des Amurlandes. _Ibid._ vol.
IV. [ii].
—— (80) Nachträge zur fossilen Flora Grönlands. _K. Svensk.
Vetenskaps-Akad. Hand._ Bd. XVIII. [_Flor. Foss. Arct._ vol.
VI. 1882.]
—— (82) Die Fossile-Flora Grönlands. _Flor. Foss. Arct._ vol. VI.
=Hegelmaier, F.= (72) Zur Morphologie der Gattung _Lycopodium_. _Bot.
Zeit._ 1872, p. 773.
=Hick, T.= (93) On a new fossil plant from the Lower Coal-Measures.
_Journ. Linn. Soc._ vol. XXIX. p. 86.
—— (93²) Supplementary note on a new fossil plant. _Ibid._ p. 216.
—— (96) On _Rachiopteris cylindrica_. _Mem. Proc. Manchester Lit.
Phil. Soc._ vol. XLI. pt. i.
=Hieronymus, G.= (02) Selaginellaceae. _Die Natürlichen
Pflanzenfamilien._ Engler and Prantl, Teil I. Abt. 4, p. 621.
=Hill, T. G.= (00) See Scott, D. H. and T. G. Hill.
—— (02) See Farmer, J. B. and T. G. Hill.
—— (04) On the presence of a parichnos in recent plants. _Annals
Bot._ vol. XVIII. p. 654.
—— (06) On the presence of a parichnos in recent plants. _Ibid._
vol. XX. p. 267.
=Hofmeister, W.= (62) On the germination, development, and
fructification of the Higher Cryptogamia, and on the
fructification of the Coniferae. _Ray Soc._ 1862.
=Hollick, A.= (94) Fossil Salvinias, including description of a new
species. _Torrey Bot. Club_, vol. XXI. No. 6, p. 253.
—— (04) Additions to the Palaeobotany of the Cretaceous Formation
on Long Island. _Bull. New York Bot. Gard._ vol. III. p. 403.
—— and =E. C. Jeffrey=. (09) Studies of Cretaceous coniferous
remains from Kreischerville, New York. _Mem. New York Bot.
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=Hooker, Sir J. D.= (48) On the vegetation of the Carboniferous
Period, as compared with that of the present day. _Mem. Geol.
Soc. Great Britain_, vol. II. pt. ii. p. 387.
—— (48²) Remarks on the structure and affinities of some
_Lepidostrobi_. _Ibid._ p. 440.
—— (59) Stangeria paradoxa. _Bot. Mag._ Tab. 5121.
=Hooker, Sir W. J.= and =J. G. Baker=. (68) Synopsis Filicum.
_London._
=Hooker, Sir W. J.= and =R. K. Greville=. (31) Icones Filicum. Vol.
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=Hosius= and =von der Marck=. (80) Die Flora der Westfälischen
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=Hovelacque, M.= (92) Recherches sur le _Lepidodendron selaginoides_,
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=Hudson, W. H.= (92) The Naturalist in La Plata. _London._
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=Jahn, J. J.= (03) Ueber die Étage H. im mittelböhmischen Devon.
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=Jeffrey, E. C.= (98) The morphology of the central cylinder in
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—— (98²) The Gametophyte of _Botrychium virginianum_. _Trans.
Canad. Inst._ vol. V. p. 265.
—— (00) The morphology of the central cylinder in the Angiosperms.
_Ibid._ vol. VI. p. 599.
—— (03) The structure and development of the stem in the
Pteridophyta and Gymnosperms. _Phil. Trans. R. Soc._ vol. CXCV.
p. 119.
—— (09) See Hollick, A. and E. C. Jeffrey.
=Jennings, A. Vaughan= and =Kate M. Hall=. (91) Notes on the
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=Jones, C. E.= (05) The morphology and anatomy of the stem of the
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=Karsten, G.= (95) Morphologische und biologische Untersuchungen über
einige Epiphytenformen der Molukken. _Ann. Jard. Buitenzorg_,
vol. XII. p. 117.
=Kidston, R.= (82) On the fructification of _Eusphenopteris tenella_
and _Sphenopteris microcarpa_. _R. Physc. Soc. Edinb._ vol. VII.
—— (83) Report on the fossil plants collected by the Geological
Survey of Scotland in Eskdale and Liddesdale. _Trans. R. Soc.
Edinburgh_, vol. XXX. p. 531.
—— (84) On a new species of _Lycopodites_, Goldenberg (_L.
Stockii_), from the Calciferous Sandstone Series of Scotland.
_Ann. Mag. Nat. Hist._ [5] vol. XIV. p. 111.
—— (84²) On the fructification of _Zeilleria_ (_Sphenopteris_)
_delicatula_, Sternb. sp.; with remarks on _Urnatopteris_
(_Sphenopteris_) _tenella_, Brongnt., and _Hymenophyllites_
(_Sphenopteris_) _quadridactylites_, Gutbier sp. _Quart. Journ.
Geol. Soc._ vol. XL. p. 590.
—— (85) On the relationship of _Ulodendron_, Lindley and Hutton,
to _Lepidodendron_, Sternberg; _Bothrodendron_, Lindley and
Hutton; _Sigillaria_, Brongniart; and _Rhytidodendron_, Boulay.
_Ann. Mag. Nat. Hist._ vol. XVI. p. 123.
—— (86²) On a new species of _Psilotites_ from the Lanarkshire
Coal-field. _Ann. Mag. Nat. Hist._ 1886, p. 494.
—— (86³) On the occurrence of _Lycopodites Vanuxemi_, Göppert, in
Britain, with remarks on its affinities. _Journ. Linn. Soc._
vol. XXI. p. 560.
—— (86⁴) Notes on some fossil plants collected by Mr R. Dunlop,
Airdrie, from the Lanarkshire Coal-field. _Trans. Geol. Soc.
Glasgow_, vol. VIII. p. 47.
—— (87) On the fructification of some ferns from the Carboniferous
formation. _Trans. R. Soc. Edinb._ vol. XXXIII. pt. i.
—— (88) See Bennie, J. and R. Kidston.
—— (88) On the fossil flora of the Radstock series of the Somerset
and Bristol Coal-field (Upper Coal-Measures). Part I. _Trans.
R. Soc. Edinb._ vol. XXXIII. pt. 2.
—— (88²) On the fructification and affinities of _Archaeopteris
hibernica_, Forbes sp. _Ann. Mag. Nat. Hist._ [6] vol. II.
—— (89) On the fossil plants in the Ravenhead Collection in the
Free Library and Museum, Liverpool. _Trans. R. Soc. Edinb._
vol. XXXV. pt. ii.
—— (89²) Additional notes on some British Carboniferous Lycopods.
_Ann. Mag. Nat. Hist._ vol. IV. p. 60.
—— (89³) On some fossil plants from Teilia quarry, Gwaenysgor,
near Prestatyn, Flintshire. _Trans. R. Soc. Edinb._ vol. XXXV.
pt. ii.
—— (91) On the fructification of _Sphenophyllum trichomatosum_,
Stern. from the Yorkshire Coal-field. _Proc. R. Soc. Edinb._
vol. XI. p. 56.
—— (91²) On the fructification and internal structure of
Carboniferous ferns in their relation to those of existing
genera. _Trans. Geol. Soc. Glasgow_, vol. IX. pt. i.
—— (91³) On the Fossil Flora of the Staffordshire Coal-fields.
II. _Trans. R. Soc. Edinb._ vol. XXXVI. p. 63.
—— (93) On _Lepidophloios_, and on the British species of the
genus. _Trans. R. Soc. Edinb._ vol. XXXVII. pt. iii. p. 529.
—— (94) On the various divisions of British Carboniferous rocks as
determined by their fossil flora. _R. Physc. Soc. Edinb._ vol.
XII. p. 183.
—— (96) On the Fossil Flora of the Yorkshire Coal-fields. I.
_Trans. R. Soc. Edinb._ vol. XXXVIII. p. 203.
—— (97) On the Fossil Flora of the Yorkshire Coal-fields. II.
_Trans. R. Soc. Edinb._ vol. XXXIX. pt. i. p. 33.
—— (01) Carboniferous Lycopods and Sphenophylls. _Trans. Nat.
Hist. Soc. Glasgow_, vol. VI. pt. i. p. 25.
—— (01²) The flora of the Carboniferous Period. _Proc. Yorks.
Geol. Polyt. Soc._ vol. XIV. pt. ii.
—— (02) The flora &c. Second Paper. _Ibid._ vol. XIV. pt. iii. p.
344.
—— (03) The fossil plants of the Carboniferous rocks of Canonbie,
Dumfriesshire, and of parts of Cumberland and Northumberland.
_Trans. R. Soc. Edinb._ vol. XL. pt. iv. p. 741.
—— (05) On the internal structure of _Sigillaria elegans_ of
Brongniart’s “Histoire des Végétaux Fossiles.” _Ibid._ vol.
XLI. pt. iii. p. 533.
—— (05²) On the fructification of _Neuropteris heterophylla_.
_Trans. R. Soc. London_, vol. CXCVII. p. 1.
—— (06) On the microsporangia of the Pteridospermeae, with remarks
on their relationship to existing Ferns. _Phil. Trans. R. Soc._
vol. CXCVIII. p. 413.
—— (07) Note on a new species of _Lepidodendron_ from Pettycur
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—— (07²) Preliminary note on the internal structure of
_Sigillaria mammillaris_ Brongniart and _S. scutellata_
Brongniart. _Ibid._ vol. XXVII. p. 203.
—— (08) On a new species of _Dineuron_ and of _Botryopteris_ from
Pettycur, Fife. _Trans. R. Soc. Edinb._ vol. XLVI. pt. ii. p.
361.
—— (08) See Gwynne-Vaughan, D. T. and R. Kidston.
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iii. p. 759.
—— (08) _Ibid._ pt. II. _loc. cit._ vol. XLVI. pt. ii. p. 213.
—— (09) _Ibid._ pt. III. _loc. cit._ vol. XLVI. pt. iii. p. 651.
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—— (02) Report on a small collection of fossil plants from the
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—— (08) Preliminary statement on the morphology of the cone of
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—— (63) See Oldham, T. and J. Morris.
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=Murchison, R. I.=, =J. Buchman=, and =H. E. Strickland=. (45)
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=Murchison, R.=, =E. de Verneuil=, and =Count A. Keyserling=. (45)
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—— (78²) Om Floran i Skånes kolförande Bildningar. _Sver. Geol.
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—— (90) Ueber das angebliche Vorkommen von Geschieben des
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—— (02) Zur fossilen Flora der Polarländer. I. Zur Oberdevonischen
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—— (02²) Beiträge zur Kenntniss Mesozoischen Cycadophyten.
_Ibid._ Bd. XXXVI. No. 4.
—— (04) Die Oberdevonische Flora des Ellesmere Landes. _Rep.
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