Marattiales (Fossil).
The discovery of Pteridosperms has necessarily led to a considerable
modification of the views formerly held that existing genera of
Marattiaceae represent survivors of a group which occupied a dominant
position in the forests of the Coal age. Mr Arber writes:—“The
evidence, formerly regarded as beyond suspicion, that the eusporangiate
ferns formed a dominant feature of the vegetation of the Palaeozoic
period, has been undermined, more especially by the remarkable
discovery of the male organs of _Lyginodendron_ by Mr Kidston. At best
we can only now regard them as a subsidiary group in that epoch in the
past history of the vegetable kingdom[983].” Dr Scott expresses himself
in terms slightly more favourable to the view that the Marattiaceae
represent the aristocracy among the Filicales. He says:—“We now have to
seek laboriously for evidence, which formerly seemed to lie open to us
on all hands. I believe, however, that such careful investigation will
result in the resuscitation of the Palaeozoic ferns as a considerable,
though not as a dominant group[984].” Zeiller’s faith[985] in the
prospect of Marattiaceous ferns retaining their position as prominent
members of Palaeozoic floras, though shaken, is not extinguished: he
recognises that they played a subordinate part.
Reference has already been made to the impossibility of determining
whether Palaeozoic fern-like fronds may be legitimately retained in
the Filicales, or whether they must be removed into the ever widening
territory of the Pteridosperms. The difficulty is that the evidence
of reproductive organs is very far from decisive. In the absence of
the female reproductive organs, the seeds, we cannot in most cases be
certain whether the small sporangium-like bodies on fertile pinnules
are true fern sporangia or the microsporangia of a heterosporous
pteridosperm. What is usually called an exannulate fern sporangium,
such as we have in _Angiopteris_ and in many Palaeozoic plants, has
no distinguishing features which can be used as a decisive test. The
microsporophylls of the Mesozoic Bennettitales produced their spores
in sporangial compartments grouped in synangia like those of recent
Marattiaceae; and in the case of _Crossotheca_, a type of frond always
regarded as Marattiaceous until Kidston[986] proved it to be the
microsporophyll of _Lyginodendron_, we have a striking instance of the
futility of making dogmatic assertions as to the filicinean nature of
what look like true fern sporangia. In all probability Dr Kidston’s
surmise that the supposed fern sporangia known as _Dactylotheca_,
_Renaultia_, _Urnatopteris_ are the microsporangia of Pteridosperms
will be proved correct[987]. The question is how many of the supposed
Marattiaceous sporangia must be assigned to Pteridosperms? There is,
however, no reasonable doubt that true Marattiaceae formed a part
of the Upper Carboniferous flora. All that can be attempted in the
following pages is to describe briefly some of the numerous types of
sporangia recognised on Palaeozoic fern-like foliage, leaving to the
future the task of deciding how many of them can be accepted as those
of ferns. It is impossible to avoid overlapping and some repetition
in the sections dealing with true Ferns and with Pteridosperms. The
filicinean nature of the stem known as _Psaronius_ (see page 415) has
not as yet been questioned.
The nomenclature of supposed Marattiaceous species from Carboniferous
and Permian rocks is in a state of some confusion owing to a lack of
satisfactory distinguishing features between certain types to which
different generic names have been assigned. As we have already seen in
the case of supposed leptosporangiate sporangia, the interpretation
of structural features in petrified or carbonised sporangia does not
afford an example of unanimity among palaeobotanical experts.
_Ptychocarpus._
This generic name, proposed by the late Professor Weiss[988],
is applied to a type of fructification illustrated by the plant
which Brongniart named _Pecopteris unita_, a species common in the
Upper Coal-Measures of England[989]. It is adopted by Kidston for
fertile specimens from Radstock which he describes as _Ptychocarpus
oblongus_[990], but the precise nature of the fertile pinnules of this
species cannot be determined.
_Ptychocarpus unita_ (Brongn.[991]). Fig. 291, A, B. (= _Goniopteris
unita_, Grand’Eury.)
This species has tripinnate fronds with linear pinnae bearing
contiguous pinnules of the _Pecopteris_ type (fig. 291, B), 4–5 mm.
long, confluent at the base or for the greater part of their length.
On the under surface of the fertile segments, which are identical
with the sterile, occur circular synangia (fig. 291, A) consisting
of seven sporangia embedded in a common parenchymatous tissue and
radially disposed round a receptacle supplied with vascular tissue.
The synangium is described as shortly stalked like those of _Marattia
Kaulfussii_ (fig. 245, B′, p. 320). In shape, in the complete union of
the sporangia, and presumably in the apical dehiscence, _Ptychocarpus_
agrees very closely with _Kaulfussia_ (fig. 245); but we cannot be
certain that we have not a collection of microsporangia simulating a
fern synangium.
A synangium closely resembling _Ptychocarpus_ has been described
by Mr Watson[992] from the Lower Coal-Measures of Lancashire as
_Cyathotrachus altus_, but there is no convincing evidence as to the
nature of the plant on which it was borne.
_Danaeites._
This generic name, instituted by Goeppert[993], has been used by
authors without due regard to the nature of the evidence of affinity to
_Danaea_. The type named by Stur _Danaeites sarepontanus_[994] (fig.
291, E) bears small pecopteroid pinnules with ovoid sporangia in groups
of 8–16 in two contiguous series on the lower face of the lamina. The
sporangia dehisce by an apical pore and are more or less embedded in
the mesophyll of the segments. No figures have been published showing
any detailed sporangial structure, and such evidence as we have is
insufficient to warrant the conclusion that the resemblance to _Danaea_
is more than an analogy.
_Parapecopteris._
_Parapecopteris neuropteroides_, Grand’Eury. Fig. 290, D.
The plant described by Grand’Eury[995] from the Coal-fields of Gard
and St Étienne, and made the type of a new genus, is characterised
by pinnules intermediate between those of _Pecopteris_ and
_Neuropteris_[996] and by the presence of two rows of united sporangia
along the lateral veins, as in _Danaea_ and _Danaeites_.
_Asterotheca._
Certain species of _Pecopteris_ fronds from Carboniferous strata
are characterised by circular sori or synangia consisting of a
small number (3–8) of exannulate sporangia attached to a central
receptacle and free only at their apices. Strasburger[997] suggested
a Marattiaceous affinity for _Asterotheca_ and Stur[998] describes
the species _Asterotheca Sternbergii_ Goepp. (fig. 291, C, D) as an
example of a Marattiaceous fern. The latter author retains Corda’s
genus _Hawlea_[999] for the fertile fronds of the common Coal-Measures
species _Pecopteris Miltoni_, while on the other hand Kidston[1000]
includes this type in _Asterotheca_.
_Pecopteris_ (_Asterotheca_) _Miltoni_ (Artis).
1825. _Filicites Miltoni_, Artis, Antedil. Phyt. Pl. XIV.
1828. _Pecopteris Miltoni_, Brongniart, Prodrome, p. 58.
1828. _Pecopteris abbreviata_, Brongniart, Hist. vég. foss. p. 337,
Pl. CXV. figs. 1–4; Lindley and Hutton, Foss. Flor. Vol. III.
Pl. 184.
1845. _Hawlea pulcherrima_, Corda, Flor. Vorwelt, p. 90, Pl. LVII.
figs. 7, 8.
1877–1888. _Hawlea Miltoni_, Stur, Culm Flora, p. 293; Farne Carbon.
Flora, p. 108, Pls. LIX. LX.
1888. _Pecopteris_ (_Asterotheca_) _abbreviata_, Zeiller, Flor.
Valenc. p. 186, Pl. XXIV. figs. 1–4.
[Illustration: FIG. 290.
A. _Alethopteris lonchitica._ × 2½. ╮ For description
B. _Lonchopteris rugosa._ × 2. ├ see Chap. XXVII.
C. _Sphenopteris Hoeninghausi._ × 4. ╯
D. _Parapecopteris neuropteroides._
E. _Pecopteris_ (_Dactylotheca_) _plumosa_ [= _P._ (_Dactylotheca_)
_dentata_ Zeiller (88)]. × 4.
(A–C, E, after Zeiller; D, after Grand’Eury.)]
The fronds of this species reached a length of more than 3 metres
and a breadth of 2 metres. They are characterised by the presence of
aphlebiae[1001] appressed to the rachis and by circular sori composed
of a small number (3–6) of sporangia. In habit and in the form of the
pinnules this type is similar to _Dactylotheca plumosa_.
[Illustration: FIG. 291.
A, B. _Ptychocarpus unita._
C, D. _Asterotheca Sternbergii._
E. _Danaeites sarepontanus._
F. _Hawlea Miltoni._
G. _Hawlea pulcherrima._
H–K. _Scolecopteris elegans._
(A, B, after Renault; C–G, after Stur; H, I, after Strasburger; K,
after Sterzel.)]
_Hawlea._
Stur[1002] retains this generic name for sori in which the sporangia
are free and united only by the proximal end to a central receptacle
(fig. 291, F, G). He describes the individual sporangia as possessing
a rudimentary annulus, a comparatively strong wall, and terminating
in a pointed distal end. He emphasises the greater degree of cohesion
between the sporangia of _Asterotheca_ as the distinguishing feature
of that genus; but this is a character difficult to recognise in some
cases, and from the analogy of recent ferns one is disposed to attach
little importance to the greater or less extent to which sporangia are
united, at least in such cases as _Asterotheca_ and _Hawlea_ when the
cohesion is never complete.
_Scolecopteris._
Zenker[1003] gave this name to detached fertile pinnules from the Lower
Permian of Saxony, which he described as _Scolecopteris elegans_. He
recognised the fern nature of the sori and suggested that the pinnules
might belong to the fronds of one of the “Staarsteinen” (_Psaronius_),
a view which subsequent investigations render far from improbable.
The sori, which occur in two rows on the lower surface of the small
pecopteroid segments with strongly revolute margins (fig. 291, H–K),
contain 4–5 sporangia attached to a stalked receptacle comparable
with that of _Marattia Kaulfussii_. These pedicellate synangia were
fully described by Strasburger[1004], who decided in favour of a
Marattiaceous alliance. The lower portions of the distally tapered
sporangia are concrescent, the distal ends being free (fig. 291,
H). Stur includes in _Scolecopteris_ the common species _Pecopteris
arborescens_ (fig. 376), but Kidston[1005] states that the British
example of _Scolecopteris_ is _S. polymorpha_, Brongn. from the Upper
Coal-Measures.
_Scolecopteris elegans_ Zenk. furnishes an example of a plant, or plant
fragment, which has been assigned to the animal kingdom. Geinitz[1006]
described silicified pinnules as _Palaeojulus dyadicus_, the generic
name being chosen because of the resemblance to Millipedes such as
the genus _Julus_. The mistake is not surprising to anyone who has
seen a block of siliceous rock from Chemnitz crowded with the small
pinnules with their concave surfaces formed by the infolding of the
edges. Sterzel[1007], who pointed out the confusion between Myriapods
and Filices, has published figures which illustrate the deceptive
resemblance of the pinnules, with their curved lamina divided by
lateral veins into segments, to the body of a Millipede (fig. 291, K).
He points out that Geinitz searched in vain for the head and legs of
_Palaeojulus_ and expressed the hope that further examination would
lead to fresh discoveries: the examination of sections revealed the
presence of sporangia and demonstrated the identity of _Palaeojulus_
and _Scolecopteris_.
_Discopteris._
Stur[1008] instituted this genus for fertile fronds from the Upper
Carboniferous Schatzlarer beds, including two species _Discopteris
karwinensis_ and _D. Schumanni_. He described the small Sphenopteroid
pinnules as characterised by disc-shaped sori made up of 70–100
sporangia attached to a hemispherical receptacle: the absence of a
true annulus led him to refer the genus to the Marattiaceae. In his
memoir on the coal-basin of Heraclea (Asia Minor), Zeiller[1009]
instituted the species _Sphenopteris_ (_Discopteris_) _Rallii_ and
figured sporangia resembling those described by Stur in the possession
of a rudimentary “apical annulus.” He compared the sporangia with
those of recent Osmundaceae and Marattiaceae. In the later memoir on
the Upper Carboniferous and Permian plants of Blanzy and Creusot,
Zeiller[1010] gives a very full and careful description of fertile
specimens of _Sphenopteris_ (_Discopteris_) _cristata_, a fern
originally described by Brongniart as _Pecopteris cristata_[1011]. Many
of the Sphenopteroid pinnules of this quadripinnate fern frond show
the form and structure of the sori with remarkable clearness in the
admirable photographs reproduced in Plates I.–III. of Zeiller’s Blanzy
memoir. The lobed pinnules of this species are of oval-triangular
form, 5–15 mm. long and 2·5–6 mm. broad[1012]. An examination of the
type-specimens of _Discopteris_ from Vienna enabled Zeiller to correct
Stur’s original description of the sori: he found that the Austrian
and French specimens, though specifically distinct, undoubtedly belong
to one genus. The sori in _Discopteris cristata_ are globular, as in
the recent genera _Cyathea_ and _Alsophila_, and frequently cover
the whole face of the lamina. The individual sporangia are 0·4–0·5
mm. long and 0·15–0·2 mm. in diameter; they are exannulate, but for
the annulus is substituted a group of thicker-walled and larger
cells in the apical and dorsal region. The description by Stur of a
hemispherical receptacle seemed to indicate an important difference
between the Austrian and French species; but Zeiller found that this
feature does not actually exist and that it was so described as the
result of misinterpretation. Zeiller succeeded in isolating spores,
40–50 μ in diameter, from some of the sporangia of _D. cristata_ and
found that they exhibited the three-rayed pattern characteristic of
fern-spores and which is indicative of their formation in tetrads. The
conclusion arrived at is that the genus _Discopteris_, as represented
by _D. karwinensis_, _D. cristata_ etc., may be regarded as a true
fern and included in the Marattiaceae. As Zeiller points out, the
sori of _Discopteris_ differ from those of recent Marattiaceae in
their pluriseriate construction and agree in this respect with those
of the Cyatheaceae. The comparison already made[1013] between the
sporangia of _D. Rallii_ and those of recent Osmundaceae holds good:
the genus affords another example of a generalised type, in this case
probably a fern, combining features which are now distributed among the
Marattiaceae, Osmundaceae and Cyatheaceae.
• • • • •
In addition to genera founded on true synangia or groups of free
or partially united sporangia, the literature of Palaeozoic ferns
contains several generic names applied to sporangia which occur
singly on Sphenopteroid or Pecopteroid pinnules. The following may
serve as examples; but it should be stated that these will probably
be transferred eventually to the Pteridosperms. It is, however,
immaterial whether they are dealt with here or in the chapter devoted
to the seed-bearing “ferns.”
_Dactylotheca._
Zeiller[1014] created this genus for fertile fronds of _Pecopteris
dentata_ Brongn. (= _P. plumosa_ Artis[1015]), a common British species
in the Upper and Middle Coal-Measures. Stur[1016] included _P. dentata_
in his list of species of _Senftenbergia_, the genus to which reference
was made under the Schizaeaceae.
_Pecopteris_ (_Dactylotheca_) _plumosa_ (Artis). Figs. 290, E, 292, 293.
1825. _Filicites plumosus_, Artis, Antedil. Phyt. p. 17, Pl. XVII.
1828. _Pecopteris plumosa_, Brongniart, Hist. vég. foss. p. 348, Pls.
CXXI. CXXII.
—— _P. dentata_, Brongniart, _ibid._ Pls. CXXIII. CXXIV.
—— _P. delicatulus_, Brongniart, _ibid_. Pl. CXVI. fig. 6.
1832. _Sphenopteris caudata_, Lindley and Hutton, Foss. Flor. Vol. I.
Pl. XLVIII.; Vol. II. Pl. CXXXVIII.
1834. _Pecopteris serra_, Lindley and Hutton, _ibid._ Vol. II. Pl.
CVII.
1834. _Schizopteris adnascens_, Lindley and Hutton, _ibid._ Vol. I.
Pls. C. CI.
1836. _Aspidites caudatus_, Goeppert, Syst. fil. foss. p. 363.
1838. _Steffensia silesiaca_, Presl, in Sternberg, Flor. Vorwelt,
Vers. II. p. 122.
1869. _Pecopteris silesiacus_, Schimper, Trait. pal. vég. Vol. I. p.
517.
—— _Cyathocarpus dentatus_, Weiss, Flora der jüngst. Stk. und
Roth. p. 86.
1877. _Senftenbergia plumosa_, Stur, Culm Flora, II. p. 187 (293).
—— _S. dentata_, _ibid._
1886. _Dactylotheca plumosa_, Kidston, Cat. Palaeozoic Plants, p. 128.
1888. _Dactylotheca dentata_, Zeiller, Flor. Valenc. Pls.
XXVI.–XXVIII.
For a fuller synonymy reference should be made to Kidston’s account of
this species[1017], from which the above list is compiled. The large
fronds of this species are tri- or quadripinnate. The pinnules vary
much in shape and size and in degree of lobing, according to their
position on the frond (fig. 293). The primary pinnae are subtended by
two Aphlebiae (fig. 293, A) appressed to the rachis, like the delicate
leaves of the recent fern _Teratophyllum aculeatum_ (see page 301). The
sporangia (0·5–0·65) are oval and exannulate and are attached parallel
to the lateral veins; they may occupy the whole of the space between
the midrib and the edge of the pinnules. This species occurs in the
Upper, Middle, and Lower Coal-Measures of Britain, reaching its maximum
in the Upper Coal-Measures. The aphlebiae undoubtedly served to protect
the young fronds, as shown by a specimen figured by Kidston (fig. 293,
B); they may also have served other purposes, as suggested by the
above comparison with _Teratophyllum_, in the mature frond. Lindley
and Hutton regarded the aphlebiae as leaves of a fern climbing up the
rachis; which they named _Schizopteris adnascens_, a confusion similar
to that already mentioned in the description of _Hemitelia capensis_
(see p. 304).
[Illustration: FIG. 292. _Dactylotheca plumosa._ (After Kidston.
Slightly reduced.)]
[Illustration: FIG. 293. _Dactylotheca plumosa_: A. Rachis with
Aphlebiae. B, _a_, young pinnae circinately folded. (After Kidston.
A, B, ⅘ nat. size.)]
_Renaultia._
This name was proposed by Zeiller[1018] for Upper Carboniferous fertile
pinnae of the Sphenopteroid type, bearing ovoid sporangia either
singly or in marginal groups of 2 to 5 at the ends of the veins. The
appearance of the apical cells occasionally suggests the presence of a
rudimentary annulus. Kidston has recorded this type of fructification
in Britain[1019]. Stur describes fertile pinnules of the same type
under the generic name _Hapalopteris_[1020].
_Zeilleria._
This genus was founded by Kidston[1021] for fertile pinnae of a very
delicate fern, _Zeilleria delicatula_ (Sternb.) characterised by
filiform ultimate segments bearing an indusium-like body, spherical
when immature and splitting at maturity into four small valves.
Kidston, in his earlier paper, compared the species with recent
Hymenophyllaceae. In the same genus he includes _Z. avoldensis_[1022]
(Stur) assigned by Stur to _Calymmatotheca_, a genus described by some
authors as characterised by groups of radially elongated sporangia at
the tips of the pinnules; these supposed sporangia are now known to be
the valves of an indusium-like organ or cupule, as Stur asserted. There
can be little doubt that the fertile fronds placed in _Calymmatotheca_
and in _Zeilleria_ were borne by Pteridosperms.
_Urnatopteris._
The Upper Carboniferous fronds of a delicate Sphenopteris habit, to
which this name was assigned by Kidston[1023], were described by
him as _Eusphenopteris tenella_ (Brongn.)[1024] and compared with
Hymenophyllaceae; subsequently Kidston expressed the opinion that
_Urnatopteris_ may be a Marattiaceous fern, as Williamson[1025]
believed; he has since suggested that the sporangia are the
microsporangia of a Pteridosperm[1026]. The sterile and fertile pinnae
differ in the absence of a lamina in the latter. The sporangia (or
microsporangia) are characterised by a poricidal dehiscence.
The records from strata higher in the geological series than the
Permian, disregarding many of doubtful value, afford ample testimony to
the existence of Marattiaceae in Upper Triassic and Rhaetic floras.
_Marattiopsis._
The generic name _Danaeopsis_ was applied by Heer[1027] to an Upper
Triassic fern, previously described by Presl as _Taeniopteris
marantacea_. A splendid specimen from the Keuper of Stuttgart is
figured in Schimper’s Atlas[1028] showing the pinnate habit of the
frond and the broadly linear segments, 25 cm. × 3·5 cm., bearing rows
of contiguous sporangia. The large pinnules have a strong midrib
giving off curved and forked lateral veins. Presl’s species may most
appropriately be included in the genus _Marattiopsis_. A specimen of
_M. marantacea_ described by Leuthardt[1029] as _Danaeopsis marantacea_
from the Upper Trias of Basel shows a peculiarity in the venation;
the lateral veins often fork near their origin, as noticed by other
authors, but each vein forks a second time near the edge of the lamina
and the two arms converge, forming a series of intramarginal loops
(fig. 265, B).
_Marattiopsis Muensteri_ (Goepp.). Fig. 245, D, E.
This widely spread Rhaetic plant affords the best example of a
post-Permian species which may be accepted as an authentic record of
fossil Marattiaceae. Various generic names have been used for this
species; Goeppert originally described the plant as _Taeniopteris
Muensteri_[1030]; Schimper[1031] proposed the name _Marattiopsis_, and
Schenk[1032] substituted _Angiopteris_ on the ground that the fertile
pinnules resemble that genus rather than _Marattia_. _Marattiopsis_, if
interpreted as indicating a _family_ resemblance rather than special
affinity to the genus _Marattia_, would seem to be the more appropriate
designation.
This species has been figured by several authors and in many instances
with fertile pinnules; the best illustrations are those published by
Zeiller[1033] in his monograph of Tonkin plants.
The pinnate fronds are characterised by a broad rachis bearing
sessile broadly linear pinnules rounded at the base, obtusely
pointed at the apex, reaching a length of 15–20 cm. and a breadth
of 12–35 mm. From a well-marked midrib are given off secondary
veins dichotomously branched close to their origin. The linear
synangia near the ends of the veins contain two rows of sporangial
compartments and open as two valves as in _Marattia_. (Cf. fig.
245, A, p. 320.)
[Sidenote: DANAEOPSIS]
This species occurs in the Rhaetic beds of Scania, Franconia, and
Tonkin. A similar type is figured by Fontaine from Jurassic beds in
California as _Angiopteridium californicum_[1034], and Bartholin[1035]
and Moeller[1036] record _M. Muensteri_ from the Lias of Bornholm.
Schenk’s species from China[1037], _Angiopteris Richthofeni_, is
a closely allied species, and a similar form is recorded from
Jurassic and Caucasian strata[1038]. The microscopical examination by
Nathorst[1039] of a group of spores from a synangium of _M. Muensteri_
shows that they resemble those of recent Marattiaceae.
• • • • •
From the Upper Triassic plant beds of Lunz, Stur has included several
species of ferns in the Marattiaceae, and of these Krasser[1040]
has recently published full diagnoses but unfortunately without
illustrations. In addition to _Marattiopsis marantacea_ (Presl) the
list includes species referred to _Coniopteris_, to _Speirocarpus_,
a genus founded by Stur, to _Oligocarpia_, _Asterotheca_, and
_Bernouillia_ (Heer).
As already pointed out, some at least of these Austrian ferns are more
probably Osmundaceous than Marattiaceous.
_Danaeopsis Hughesi_, Feistmantel.
The pinnate fronds described by Feistmantel[1041] from the Middle
Gondwana rocks of India and recorded from Rhaetic strata in South
Africa[1042], China[1043], and Tonkin[1044], may belong to a member of
the Marattiaceae, but no fertile specimens have been described. The
close agreement between the sterile leaves from India and South Africa
and the fertile fronds of _Marattiopsis marantacea_ suggests generic
identity.
The Upper Triassic ferns described by Heer, Krasser[1045],
and Leuthardt[1046] as _Bernouillia_ have been referred to the
Marattiaceae, but without trustworthy evidence in favour of this
affinity.
The large leaves, 70 cm. long and 7 cm. broad, described by Zigno[1047]
from the Jurassic of Italy as _Danaeites Heeri_, are probably Cycadean.
The Polish Jurassic species _Danaea microphylla_[1048] is a more
satisfactory record.
[Illustration: FIG. 294.
A, B. _Nathorstia angustifolia_, Heer. (After Heer. A, nat. size.)
C, D. Sorus of _N. latifolia_, Nath. (After Nathorst. C, × 12;
D, × 45.)]
_Nathorstia._
This name was instituted by Heer[1049] for pieces of pinnate fronds
from Lower Cretaceous rocks of Greenland. The resemblance of the long
pinnules to the fertile segments of _Laccopteris_ is so close that
generic identity might well be assumed, but it has recently been
shown by Nathorst[1050] that the soral characters justify Heer’s
use of a distinctive name for the Arctic fern. The circular sori
arranged in two rows (fig. 294, A, B) are superficially identical with
those of _Laccopteris_, but consist of concrescent sporangia forming
a circular synangium (fig. 294, C, D) like those of _Kaulfussia_
and _Ptychocarpus_. The lighter areas in fig. 294, D, represent
the sporangia: fig. C shows the radial disposition of the numerous
sporangial compartments round a central receptacle. From a stout midrib
lateral veins arise at right angles, but their distal terminations are
not preserved. It is probable, as Nathorst suggests, that Bayer’s[1051]
species _Drynaria fascia_ from the Lower Cretaceous rocks of Bohemia
should be referred to Heer’s genus. In the absence of well-preserved
sori it would be exceedingly difficult, or even impossible, to
distinguish between pinnules of _Laccopteris_ and _Nathorstia_.
A Tertiary species, _Marattia Hookeri_ (fig. 261, C, p. 350), described
by Gardner and Ettingshausen[1052] from the Eocene beds of the Isle of
Wight is referred by them to the Marattiaceae because of a resemblance
of the sterile pinnae to those of _M. Kaulfussii_; but this is
insufficient evidence of relationship.