CHAPTER XXXVII.

BENNETTITALES (_continued_).

=WILLIAMSONIA.= Carruthers.

This genus was first figured by Young and Bird[1192] from specimens

obtained from Lower Estuarine beds near Whitby: these authors compared

the fossils to the head of an Artichoke (_Cynara integrifolia_), ‘the

covering or calyx consisting of numerous lanceolate and striated

leaves’ (fig. 544). In 1840 Williamson[1193] noticed the association

with fronds of _Zamia gigas_ Lind. and Hutt. of ‘a remarkable fossil,

apparently connected with the fructification of a _Cycas_,’ and some

years later Yates[1194] expressed the opinion that the fructifications

figured by Young and Bird probably belonged to the plants which

bore the fronds known as _Zamites gigas_. Leckenby[1195] figured

some leaves of _Palaeozamia pecten_ (= _Ptilophyllum pecten_) in

close association with a small flower of _Williamsonia_ which was

subsequently recognised as a whorl of microsporophylls. In 1870 two

papers of exceptional interest were published, one by Williamson[1196]

who was the first to attempt an exhaustive account of the genus, and

the other by Carruthers[1197] who proposed the name _Williamsonia_,

thus associating ‘with a group of the most characteristic Yorkshire

fossils two men (father and son) who have largely contributed to the

exposition of Yorkshire geology.’ Carruthers instituted a new tribe

Williamsonieae for the genus _Williamsonia_, the type-species being

_Williamsonia gigas_: the specific name had been previously given by

Lindley and Hutton to the fronds (_Zamia gigas_) of the plant which

was believed to have borne the flowers for which the new designation

was proposed. Two other species, _Williamsonia hastula_ and _W.

pecten_, were assigned to the new genus. The conclusion arrived at by

Williamson as to a connexion between _Zamites gigas_ and _Williamsonia_

flowers was, however, not accepted by Saporta[1198], who figured and

described several exceptionally good specimens from the Yorkshire coast

which formed part of the Yates collection in the Paris Natural History

Museum. In 1897 a short account was published[1199] of the Yates

specimens, an examination of which convinced me of the correctness of

Williamson’s views as to an organic connexion between stems, peduncles,

flowers, and fronds. During a visit to Paris several photographs were

taken, but these were not published: similar photographs have since

been reproduced by Wieland[1200] and reduced copies from two negatives

in my possession are shown in figs. 541, 542. The restoration by

Williamson in his well-known memoir is probably correct so far as the

general habit of the plant is concerned, though the flowers which

he speaks of as male are now known to be ovulate. The position of

the male organs, whether borne separately or on the same axis as the

megasporophylls, has not been definitely settled.

In 1891 the Marquis of Saporta thus introduced his discussion on

Williamsonia,—‘avec les _Williamsonia_ nous abordons un des problèmes

les plus difficiles, un des sujets des plus controversés, mais

aussi les plus curieux, peut-être même le plus remarquable de tous

ceux que nous offre l’ensemble des plantes jurassiques.’ Wieland’s

investigations have placed us in possession of many important

facts with regard to the closely allied flowers of _Cycadeoidea_

and have enabled us considerably to extend our knowledge beyond

the stage represented by the work of Carruthers, Williamson, and

other authors; and more recently Nathorst’s important discoveries

have demonstrated the close agreement between _Williamsonia_ and

_Bennettites (Cycadeoidea)_. Several problems still remain unsolved.

Having regard to the deficiency of the data concerning the morphology

of the _Williamsonia_ type of flower and the wider question as to

a phylogenetic relationship that some botanists believe to exist

between the Bennettitales and the Angiosperms, Saporta’s words

are still pertinent. Wieland’s discoveries in Mexico[1201] have

furnished additional evidence of the wide geographical distribution

of the _Williamsonia_ type of flower in the Jurassic period, and it

may be confidently asserted that the Bennettitales, including both

_Williamsonia_ and _Cycadeoidea_, occupied a dominant position in the

floras of the world during the stage of plant-development immediately

preceding the evolution and rapid spread of the Angiosperms, the

present dominant class.

There has been considerable uncertainty among authors with regard to

the application of the name _Williamsonia_. In former accounts of the

genus the name was employed by me both for leaves and flowers on the

ground that Williamson was correct in his opinion as to the connexion

between _Williamsonia gigas_ and _Zamites gigas_. The type of frond to

which the latter term is applied is by no means uncommon in Jurassic

strata though it is not always associated with flowers, and the

use of the generic term _Williamsonia_ is therefore not invariably

justifiable. Nathorst[1202] has recently reiterated his opinion that it

is inadvisable to employ the name _Williamsonia_ except for the flowers

or the complete plant and strongly urges palaeobotanists to retain

the provisional genus _Zamites_ when the fronds only are in question.

While agreeing with the contention that the greatest care should be

exercised to avoid the use of generic names implying a correlation of

vegetative and reproductive organs that rests on any evidence short of

demonstration, it may be suggested that the better plan is to add the

name _Williamsonia_ in parentheses after _Zamites_ or _Ptilophyllum_

in cases where there is no reason to doubt that the fronds belong to a

_Williamsonia_ plant.

_Williamsonia gigas_ (Williamson).

The species selected for a rather detailed description is still

imperfectly known, but it is particularly interesting as the type on

which the first scientific account of the genus was based. The name

_Williamsonia gigas_ is now generally employed for the flowers which

bore megasporophylls as the essential organs: they may have been

bisporangiate,—a view that seems to me the more probable,—but this

has not been demonstrated. There are very few cases in which fronds of

_Zamites gigas_ occur in organic connexion with stems, and we cannot

with safety employ other than a provisional generic term for fossil

stems which it is believed bore flowers of the _Williamsonia_ type.

For the imperfectly preserved piece of stem shown in fig. 541 the

name _Williamsonia (Bucklandia) gigas_ is employed, as there is no

reasonable doubt that in addition to the fronds of _Zamites gigas_ it

bore peduncles (fig. 541, _a_), with _Williamsonia_ flowers. This and

other stems found in close association with _Williamsonia_ flowers in

England, India, and Mexico are of the type known as _Bucklandia_[1203];

but it would in most instances be unwise to add _Williamsonia_ even as

a subordinate title. Casts of stems in close association with fronds

and flowers are not uncommon in

collections of plants from the Yorkshire coast; the surface-features

are of the type shown in fig. 576, rhomboidal or lozenge-shaped bases

of petioles as described under the genus _Bucklandia_[1204]. The stem

reproduced in fig. 541, about 5 cm. broad, is imperfectly preserved and

the leaf-bases are not clearly seen. Saporta’s figure[1205] conveys

but a poor idea of the actual specimen. To one side of the stem, 5 cm.

from the lower, broken, end, are attached the petioles of two clearly

preserved fronds of _Zamites gigas_, and above these is part of a third

frond apparently in its original position. The main axis is prolonged

obliquely upwards to the left as a branch, _a_, 3 cm. broad and 14 cm.

long, covered with hairy bracts and bearing distally several narrow,

linear-lanceolate, scale-leaves. This branch is undoubtedly a fertile

shoot or peduncle. A specimen figured (from a drawing) by Saporta[1206]

as a peduncle of a _Williamsonia_ flower and reproduced in fig. 542 is,

in surface-features, identical with the branch _a_ shown in fig. 541,

but at the apex it bears a bud covered with linear bracts identical

with those of _Williamsonia gigas_. This bud is almost certainly a

young flower. Similar peduncles are described by Williamson, and he

speaks of one which is bifurcated: this specimen is probably that

reproduced in fig. 543 and now in the Leeds Museum: at the base the

axis is 3·5 cm. in diameter; the two divergent arms bear numerous

bracts identical with those of _Williamsonia gigas_ and in addition

are a few shorter ovate scales recalling those figured by Nathorst as

probably belonging to _Williamsonia pecten_. The Leeds specimen is

from the Lower sandstone and shale near Scarborough. Similar branched

peduncles are represented in the Whitby Museum and in the National

Collection. Wieland[1207] has also figured a peduncle bearing a

‘typical fruit bud’ of _Williamsonia gigas_ similar to that reproduced

in fig. 542. These specimens fully justify Williamson’s restoration

published in his paper of 1870.

[Illustration: Fig. 541. _Williamsonia gigas._ Fronds (_Zamites

gigas_) and flowering shoot, _a_, attached to a stem (_Bucklandia_).

(Yates Collection, Paris; nat. size.)]

[Illustration: Fig. 542. _Williamsonia gigas._ Flowering shoot and

flower-bud. (Yates Collection, Paris.)]

In a former account of this species[1208] the opinion was expressed

that the flowers described by Williamson as male were ovulate and

constructed on the plan of those of _Bennettites Gibsonianus_

Carr. This conclusion has since been confirmed by Nathorst[1209]

who succeeded in obtaining excellent preparations of the cuticular

membranes of interseminal scales and micropylar tubes (fig. 545),

demonstrating their very close agreement with those of the flowers of

_Cycadeoidea_.

[Illustration: Fig. 543. _Williamsonia gigas._ Two peduncles, B and

C, with imperfectly preserved bracts. Diameter of axis, A, 3·5 cm.

(From a specimen in the Leeds Museum; nat. size.)]

One of Williamson’s ‘carpellary discs’ has been shown by Nathorst to be

a verticil of microsporophylls bearing synangia, but both this author

and Lignier[1210] think that the two specimens figured by Williamson as

carpellary discs are distinct organs, one being a staminate whorl and

the other a sterile infundibuliform organ. My own view is that both are

of the same nature and consist of microsporophylls.

[Illustration: Fig. 544. _Williamsonia gigas._ Portion of a flower

showing the protective bracts, the annular zone formed by numerous

sterile sporophylls and interseminal scales, and the large central

cavity originally occupied by the receptacle. (From a specimen in the

Williamson collection, Cambridge Botany School; nat. size.)]

[Illustration: Fig. 545. _Williamsonia gigas._ Micropylar tube.

(After Nathorst.)]

Fig. 544 represents the usual form in which the flowers of _W. gigas_

are found; it consists of linear bracts covered with hairs identical

with those on the peduncles shown in figs. 541–543; they surround a

pyriform axis and form what Williamson called an involucrum. The base

of the fossil is characterised by an annular zone formed of crowded,

radially disposed, narrow ridges now known to be casts of interseminal

scales. At the outer edge of this annular area impressions of the

peltate ends of interseminal scales are not infrequently preserved.

Fig. 545 is a photograph of one of Nathorst’s preparations showing

the very great similarity between a micropylar tube of _W. gigas_ and

the corresponding structures in _Cycadeoidea_. The small micropylar

tubes are surrounded by 5–6 polygonal expanded apices of interseminal

scales as in _Cycadeoidea_ (fig. 515; _cf._ also fig. 563), and the

apex of each peltate distal end projects slightly as a central papilla

composed of more strongly cuticularised cells. In most specimens the

megasporophylls and interseminal scales (sterile megasporophylls) are

preserved only as an annular zone at the base of the receptacle (fig.

548, _as_), but it is clear from some specimens of _W. gigas_ and other

species figured by Saporta[1211], Nathorst[1212], and Krasser[1213]

that originally the whole surface of the pyriform axis was beset with

these organs which fell off, presumably, when the seeds had reached

maturity. No satisfactory examples of seeds have been found in English

specimens. Krasser has described some specimens of _Williamsonia_

from Jurassic rocks in Sardinia to which he assigns some associated

seeds, but, as he admits, there is no proof of any connexion. In some

cases a funnel-like depression is seen at the upper end of a strobilus

of _W. gigas_ (fig. 546, B, C, _a_) identical in the occurrence of

radially disposed ridges with the annular zone at the base and due to

the preservation of interseminal scales and aborted megasporophylls in

the upper part of the receptacle: in this region also the impressions

of polygonal apices of the scales are sometimes found. The probability

is that while the greater part of the armour of scales and seeds was

thrown off, at the upper and lower end of the receptacle some sterile

megasporophylls and scales remained (fig. 548, _as_, _dl_).

[Illustration: Fig. 546. _Williamsonia gigas._ A, apical portion

of flower. B, cast of A; _a_, persistent interseminal scales. C,

flower in longitudinal section. C′, interseminal scales from the base.

(Williamson Collection, Botany School, Cambridge.)]

Williamson regarded the funnel-shaped depression as the impression of

the lower surface of a laterally expanded portion of the axis of the

flower, and to this expansion he gave the name lenticular disc (figs.

546, 547, _a_). It is, however, much more likely that the apparent

extension of the axis is due to the preservation of the sterile

zone of armour which formed a cluster of appendages, the impressions

of which are seen on the sides of the funnel-like depression, the

receptacle being prolonged as a slender axis (fig. 547, C). The next

point to consider is the form of the axis beyond the level of the

collar of sterile armour. Williamson described the axis as spreading

out to form the lenticular disc and then prolonged as a narrow conical

pyramidal axis which is slightly extended horizontally immediately

below a terminal mammilla: the apical mammilla he designated the

corona (fig. 547, C, _r_). As already stated, the lenticular disc

is probably not an expanded part of the axis but the result of the

preservation of a spreading mop-like cluster of interseminal scales.

This is the view expressed by Lignier[1214] who kindly furnished

the block from which fig. 548 is reproduced. The lower face of

Williamson’s lenticular disc is characterised by a series of spoke-like

radiating ridges (fig. 547, A′) between which are less distinct

radially disposed lines, and at the periphery there are impressions

(fig. 547, A′′), continuous with some of the radiating ridges, of the

terminal shields of interseminal scales. In fig. 547, drawn from one

of the original specimens described by Williamson, these features are

shown at A′ and B: fig. A′ represents the circular area, which is

at right-angles to the axis of the flower, in surface-view. In the

centre of this circular area is a depression ending in a short papilla

surrounded by a narrow basal rim: this feature is shown on a cast of

the specimen represented in fig. 547, B. In this case Williamson’s

corona is seated on a very short axis whereas in fig. 547, C, also from

one of Williamson’s specimens, the corona forms the apex of a longer

pyramidal axis. Wieland[1215] regarded the circular area seen in fig.

547, A, as the impression of the apical portion of a bisporangiate

strobilus, the ridges marking the edges of the incurved distal portions

of microsporophylls bent over the apex of the ovulate cone (_cf._ fig.

513), and he interpreted the polygonal depressions at the periphery

(fig. 547, A′′) as those of sori, an interpretation entirely different

from that of Lignier. The latter author[1216] in part reasserted his

opinion but modified it as regards the meaning of the ridges on the

circular area, agreeing so far with Wieland as to consider them as

having been formed by the folded-over rachises of microsporophylls

attached as a concrescent collar to the base of the ovulate cone. This

interpretation does not, however, explain the relation between the

radial striations on the circular area and the polygonal impressions

at its periphery. Wieland still dissents from Lignier’s opinion and

suggests that the circular area has not been demonstrated to belong

to the apical end of a flower. Fig. 547 shows that its position is

apical. Fig. 548 represents Lignier’s view as to the nature of the rim

surrounding the apical mammilla: he suggested that several interseminal

scales borne at the apical region of the receptacle were concrescent

and formed linear bracts the edges of which are represented by the main

ridges in fig. 547, A′. These concrescent scales bent upwards and were

closely applied to or perhaps concrescent with the pyramidal axis and

were then prolonged as a wide infundibuliform apparatus (Williamson’s

carpellary disc). This organ was, however, easily detached, and the rim

seen at _r_ in fig. 547, C, represents its narrow broken base. With

this view I am in general agreement; but while Lignier regards the

funnel-like appendage as sterile and considers that similar organs,

but with a large central cavity at the base of the funnel, may have

been microsporophyll-discs which were borne below the ovulate strobilus

in the position occupied by the microsporophylls in _Cycadeoidea_

(fig. 528)—my inclination is to see in the terminal appendage a

whorl of concrescent microsporophylls. This view lacks the support

of demonstration. It is obvious from Williamson’s specimens and from

others described by Saporta, Nathorst, and Lignier that the receptacle

of _Williamsonia gigas_ was not so simple in its termination as that

of the flowers of _Cycadeoidea_. In _Cycadeoidea dacotensis_ Wieland

showed that the apex of the receptacle bore a tuft of long interseminal

scales, and it is readily conceivable that these apical appendages

were still further developed in some _Williamsonia_ flowers to form a

whorl of concrescent leaves borne on the prolonged apex of the axis.

There is little doubt as to the homology of interseminal scales and

microsporophylls, and there is no difficulty in supposing that while in

some flowers the foliar organs assumed the form of interseminal scales

of unusual length, in other species they became microsporophylls.

[Illustration: Fig. 547. _Williamsonia gigas._ A, flower in

longitudinal section, showing, especially on the left side,

interseminal scales and megasporophylls and a pyriform cavity

representing the central axis (nat. size). A′, the under surface of

the apical region. A′′, interseminal scales from A′. B, cast of A′.

C, apical region of another specimen; _a_, interseminal scales; _c_,

column; _r_, ridge. (Williamson Collection, Botany School, Cambridge.)]

[Illustration: Fig. 548. _Williamsonia gigas._ Restoration showing

an ovulate strobilus bearing a terminal infundibuliform appendage.

Lignier, to whom the restoration is due, points out that the apical

portion of the axis at _dl_ should be represented as straight and not,

as in the figure, horizontally expanded. _bi_, bracts; _as_, persistent

interseminal scales forming the annular zone; _r_, receptacle; _cs_,

caducous megasporophylls and interseminal scales; _dl_, persistent

interseminal scales, an extension of which formed the large funnel-like

appendage, _at_; _ap_, apex of the receptacle. (After Lignier.)]

It is noteworthy that the radiating ridges on the circular area

shown in fig. 547, A′, agree in position and approximately at

least in number with those on the sides of the cupular disc of

the microsporophyll-verticil of _Williamsonia whitbiensis_[1217].

Nathorst describes a specimen seen in a private collection in which

an infundibuliform appendage appeared to be preserved in situ at the

apex of a flower of _Williamsonia gigas_ (_cf._ fig. 548, _at_).

Thomas[1218], in his description of _Williamsoniella_, compares

the radial ridges on the apical sterile portion of a flower of

_Williamsonia gigas_ to the ridges on his _Williamsoniella_ which are

formed by the tips of infolded microsporophylls.

[Illustration: Fig. 549. _Williamsonia gigas._ A, diagrammatic

drawing showing the position of the synangia, at _S_, and part of the

staminate disc. B, a single synangium; × 6. (After Thomas.)]

_Williamsonia gigas_ (Microsporophylls).

[Illustration: Fig. 550. _Williamsonia gigas._ Side-view of an

incomplete staminate disc showing the basal cup torn at the lower end

and part of one of the free microsporophylls. (Diagrammatic drawing,

after Thomas; nat. size.)]

In the course of an examination of the _Williamsonia_ specimens (from

Yorkshire) in Paris in July of last year (1914) Mr Thomas[1219]

found a specimen previously overlooked, which is undoubtedly either

a male flower or, as I am inclined to think, the staminate disc of a

bisporangiate flower of _Williamsonia gigas_. The nature of the matrix

shows that it came from the neighbourhood of Whitby. It consists

of an urn-shaped organ formed of the concrescent bases of 18–20

microsporophylls each 7–8 mm. wide; the cup is 5–6 cm. broad, the

base being torn but tapered (fig. 549) as though originally prolonged

downwards into a stalk as in _W. spectabilis_. Along the middle line

of each sporophyll is a series of depressions, probably the same in

nature as those on _W. whitbiensis_ described by Nathorst, though it

is not clear whether, in this case at least, they represent aborted

synangia. Some reniform synangia (fig. 549, B) occur in the rock just

above the cup. The sporophylls spread outwards from the base and then

curve inwards, bending outwards again as they become free. A portion

of a microsporophyll is shown in fig. 550 bearing segments projecting

inwards as in _W. spectabilis_ (fig. 551). This specimen, which occurs

in association with female flowers, is regarded by Mr Thomas as part

of a unisexual flower. He discusses the possibility of its connexion

with an ovulate receptacle and expresses the opinion that if it were

borne at the upper end of a bisporangiate flower the whole would be

top-heavy and the arrangement uneconomical. On the other hand if, as

suggested on page 434, the flowers were bisexual the staminate disc,

which reached maturity before the ovules, may have been thrown off,

as in _Cycadeoidea_, before the seeds were ripe. The form of the disc

resembles that of the Indian specimen described on another page as

_Williamsonia_ sp., _cf._ _W. setosa_ Nath.; it does not, I venture to

think, afford an argument against the view that the microsporophyll-cup

of some _Williamsonia_ flowers was attached near the apex of the

receptacle and was formed of modified foliar organs homologous with

those which, in the ovulate portion of the flower, constitute the

interseminal scales and megasporophylls.

A further consideration of the microsporophylls of _Williamsonia_ will

be found in a later section of this chapter.

_Williamsonia spectabilis_ Nathorst.

This species[1220], the first example of undoubted microspore-bearing

organs referred to _Williamsonia_, was founded on material discovered

by Prof. Nathorst in the Lower Estuarine series of Whitby; it has also

been obtained from beds of the same age at Marske in the Cleveland

district of Yorkshire[1221]. _Williamsonia spectabilis_, though

indubitably a male organ, has not been found attached to a stem, and

there is no decisive evidence as to its connexion with a particular

species of frond. Nathorst believes that it belongs to the plant which

bore the leaves known as _Ptilophyllum pecten_, an opinion based

chiefly on association. The more complete specimens consist of a broad

funnel-shaped organ prolonged below into a slender stalk and divided at

the margin into several linear-lanceolate segments (microsporophylls)

the apices of which were rolled inwards like young fern-fronds (figs.

551, 552). The synangia agree closely in form and in such structural

features as can be made out from cuticular preparations with those

described by Wieland in American species of _Cycadeoidea_; they are

slightly reniform, 5–6 mm. long and 2 mm. broad and divided into

several loculi by transverse partitions (fig. 552). The microspores,

58–65_µ_ in length, are rather narrow, ovate and very similar to those

described by Solms-Laubach[1222] in _Cycadeoidea etrusca_. The synangia

are attached in two rows to slender lateral segments which appear to

be given off from the upper face near the median line of the broad

linear sporophylls (fig. 565, A). Nathorst points out that the position

of the fertile pinnae brings the sporophylls into close relation with

the vegetative fronds of _Ptilophyllum pecten_ and other Cycadean

fronds in which the pinnae are attached to the upper face of the

rachis. While the longer pinnae in the middle portion of a sporophyll

bear several synangia, those near the base and apex are shorter and,

in the proximal region nearer the broad cup formed by the coherent

bases of the sporophylls, occur singly, thus approaching the condition

characteristic of _W. whitbiensis_ (fig. 565, B) in which they are

sessile on the simple microsporophylls. It is noteworthy that in some

specimens figured by Nathorst there is a tendency of the lower part

of the cup to break away from the coherent bases of the sporophylls

(fig. 551)[1223], and it is not unlikely that some of the impressions

described as infundibuliform appendages are incomplete examples of

_Williamsonia spectabilis_.

[Illustration: Fig. 551. _Williamsonia spectabilis_ and leaves of

_Ptilophyllum pecten_. (After Nathorst; ⅚ nat. size.)]

[Illustration: Fig. 552. _Williamsonia spectabilis._ Restoration of

an almost mature male flower. (After Thomas; approximately nat. size.)]

[Illustration: Fig. 553. _Williamsonia Leckenbyi._ Surface-view and

in section.

(Restoration after Nathorst.)]

_Williamsonia Leckenbyi_ Nathorst.

This species, founded on specimens from the Middle Estuarine

beds exposed on the Yorkshire coast at Cloughton Wyke[1224], is

characterised by the almost spherical form of the strobilus, 4·5–5 cm.

in diameter. The relatively small receptacle is covered by a thick

mass of megasporophylls and interseminal scales except in the lower

part which bears only sterile scales. Nathorst believes that the seeds

were very small, but no undoubted examples have been found. A specimen

in the British Museum, figured in 1900[1225], shows the surface-view

of an impression of the base of the flower; a small circular raised

boss occupies the centre—the scar of the receptacle—and surrounding

this is a reticulum formed by the impression of the distal ends of the

interseminal scales. The uniform nature of the reticulum, the meshes

of which are all of the same type, shows that in the basal region of

the flower the organs borne on the receptacle were all sterile as in

_Cycadeoidea (Bennettites) Morierei_. Except in the smaller diameter

of the receptacle this specimen is practically identical with that of

_Williamsonia Carruthersi_ Sew. reproduced in fig. 559. The form of

the strobilus is shown in Nathorst’s restoration[1226] represented

in fig. 553. The interseminal scales have broad peltate distal ends

characterised by a patch of lighter and thinner-walled cells at the

apex (fig. 554); the micropylar tubes are slightly expanded at the

summit and their epidermal cells are papillose as in _Williamsonia

scotica_ (_cf._ fig. 563, B). Nathorst in 1909 adopted the name

_Williamsonia pecten_ Carr.[1227] for the specimens originally referred

to _W. Leckenbyi_ as well as for microsporophylls that he believed

to belong to the same plant as the ovulate strobili: but in a later

paper[1228] he restricts the name _Williamsonia pecten_ to the male

strobili, reserving _W. Leckenbyi_ for the ovulate forms, as there is

no proof that both were borne on the same plant. From the evidence

at present available it is reasonable to regard _W. Leckenbyi_ as a

unisexual flower. In all probability the fronds known as _Ptilophyllum

pecten_ are the foliage of the parent-plant of _W. Leckenbyi_, though

in the absence of proof it is advisable to retain both names.

[Illustration: Fig. 554. _Williamsonia Leckenbyi._ Micropyle and

interseminal scale.

(After Nathorst.)]

_Williamsonia whitbiensis_ Nathorst.

Under this name Nathorst[1229] described some interesting specimens of

microsporophylls formerly attributed by him to _Williamsonia pecten_,

but the discovery of additional material led him to distinguish the

Whitby (Lower Estuarine) fossils as _W. whitbiensis_, retaining the

name _W. pecten_ for the type originally figured by Leckenby[1230]

from the Middle Estuarine series at Cloughton Wyke on the Yorkshire

coast. In the type-specimen, 8–10 cm. in diameter, there are 15

linear segments coalescent basally into a thick cup differing from

that of _W. spectabilis_ in the absence of a stalk (figs. 555, 556).

A more important distinctive feature is the production of synangia

on the simple sporophylls (figs. 556, B; 565, B) and not on special

fertile segments as in _W. spectabilis_ (fig. 552). The inner face of

each sporophyll, as seen in impressions, shows two regular rows of

small depressions, one on each side of the median line; these become

gradually smaller towards the base of the cup-like disc (figs. 555,

556). On the actual carbonised surface of the inner face of the cup

small and transversely elongated projections take the place of the

depressions and these show the same decrease in size when traced from

the free segments to the cupular organ. Nathorst obtained microspores

only from the larger projections and none from the smaller, a

circumstance which may indicate that only the upper and larger synangia

were fully developed[1231].

[Illustration: Fig. 555. _Williamsonia whitbiensis._ (After Nathorst;

⅚ nat. size.)]

[Illustration: Fig. 556. _Williamsonia whitbiensis._ A, male flower.

B, sporophyll with synangia. (After Nathorst.)]

This species is especially interesting as throwing light on the nature

of one of the specimens (from the Whitby Museum) figured by Williamson

as a ‘carpellary disc[1232]’: the ‘seeds’ of Williamson are no doubt,

as Nathorst believes, synangia, while the smaller pairs of markings

figured by Williamson represent rudimentary synangia and not ‘abortive

ovules.’ Though the specific identity of Williamson’s specimen and

_Williamsonia whitbiensis_ is not certain, the latter is undoubtedly a

closely allied form of a microsporophyll-verticil. A specimen figured

in 1900 as a flower of _Williamsonia pecten_[1233], designated by

Nathorst _Williamsonia_ sp., is a very similar if not an identical

type; it consists of a fairly deep basal cup the surface of which is

characterised by the presence of several regular ridges between which

are pairs of small depressions containing carbonaceous matter. In the

light of Nathorst’s researches it is clear that this is an incomplete

example of a whorl of microsporophylls. The base of the disc is

incomplete, but it is certain from the small size of the basal hole

with torn edges that the cup could not have been attached to the base

of a receptacle as are the microsporophylls in Wieland’s bisporangiate

flowers of _Cycadeoidea_. The specimens referred by Nathorst to

_Williamsonia pecten_[1234] (Leck. _ex parte_) are similar to those

described as _W. whitbiensis_, but differ in the texture of the cup and

in the degree of cuticularisation of the synangial walls. The synangia

of _W. pecten_ are of the usual reniform type and multicellular as in

_W. spectabilis_.

_Williamsonia setosa_ Nathorst.

The distinguishing features of this species[1235], founded on material

collected by Dr Halle from Lower Estuarine beds at Whitby, are (i)

the greater number of linear sporophylls which bear numerous bristles

or stout hairs, (ii) the loose coherence of the contracted proximal

portion of the linear segments, and (iii) a narrower basal disc in

place of the deeper cup of other species. One of the specimens referred

to this species, formerly regarded by Nathorst as an infundibuliform

organ of an ovulate strobilus of _W. gigas_[1236], bears a striking

resemblance to an Indian fossil described by Feistmantel from

India[1237].

+Indian species of Williamsonia (Flowers).+

Several specimens of _Williamsonia_ have been described from the

Rajmahal and other Jurassic series in India, some of which exhibit a

close agreement with _Williamsonia gigas_. It is, however, noteworthy

that no fronds of the _Zamites gigas_ type have been discovered in

Indian beds; on the other hand the association of fronds of the

same type as _Ptilophyllum pecten_ with Williamsonian strobili is

significant, as also the occurrence of stems apparently identical in

surface-features with English and Mexican species.

_Williamsonia_ sp.

Oldham and Morris[1238] figured a specimen from the Rajmahal Hills

consisting of a circular disc enclosed by a zone of ‘closely packed

tubes,’ the basal portion of an ovulate Williamsonia strobilus,

which they regarded as a pressed mass of young leaves ‘probably

related to _Palaeozamia_’ [_Ptilophyllum_]. The figured specimen

shows that the radially disposed ‘tubes’ surrounding the circular

area are interseminal scales some of which are seen at the periphery

in surface-view as small polygonal areas as in English specimens.

Feistmantel[1239] refigured this specimen and referred it to

_Williamsonia gigas_ though on insufficient grounds. To the same

species Feistmantel[1240] assigns two other specimens from the

Rajmahal series, one of which consists of several narrow linear

bracts partially enclosing a strobilus with a portion of the annular

zone at the base in which the seminiferous scales are shown in

longitudinal-view and a few in apical-view.

_Williamsonia_ sp. _cf._ _Williamsonia setosa_ Nathorst.

[Illustration: Fig. 557. _Williamsonia_ sp. A, whorl of

microsporophylls; _s_, synangia (?). C, side-view of the basal portion

of A. B, part of a microsporophyll enlarged. (Indian Geological Survey;

A, nat. size.)]

A third example from the same locality (fig. 557) is described

by Feistmantel[1241] as part of one of Williamson’s ‘carpellary

discs[1242],’ a comparison that is fully justified. The accompanying

drawing has been carefully made from the actual specimen: portions of

10 very hairy bracts radiate in a horizontal plane from a continuous

lamina with a wrinkled and ridged surface bent sharply back at

right-angles to the bracts and forming a double curve as seen in the

sectional view (fig. 557, C). The form assumed by the vertical part

of the disc is, I believe, the result of compression. Wieland[1243]

regards this fossil as a whorl of microsporophylls originally attached

to the lower portion of the receptacle of a bisexual flower. Close to

the edge of one of the bracts is an imperfectly preserved structure

(fig. 557, B, _s_) which may represent two alternately arranged rows of

synangia belonging to one of the hairy bracts; but we have no evidence

as to the position of the microsporophylls on the flower-axis. The

central space enclosed by the crushed concrescent portion of the disc

is large enough to have embraced a receptacle but, on the other hand,

the portion preserved may have broken off from a proximal cup like

that of _W. spectabilis_[1244], which, as Nathorst’s specimens show,

is sometimes broken across near the upper edge of the basal funnel.

This specimen is spoken of by Feistmantel as _Williamsonia gigas_. It

is impossible to say whether these Rajmahal specimens belong to one

species, and they are therefore provisionally designated _Williamsonia_

sp. and _Williamsonia_ sp. _cf._ _W. setosa_.

_Williamsonia microps_ Feistmantel.

This species is based on a compressed ovate strobilus surrounded by

linear bracts and a portion of the cylindrical axis[1245]. It is

possible that this smaller, bud-like, specimen may be a younger example

of the species referred by Feistmantel to _Williamsonia gigas_.

_Williamsonia Blandfordi_ Feistmantel.

Founded on a small strobilus enclosed by linear bracts, from the

Jurassic rocks of Cutch[1246], very similar to _Williamsonia pecten_;

as seen in fig. 558, drawn from the original specimen, the flower is

associated with a _Ptilophyllum_ frond indistinguishable from some

examples of _Ptilophyllum pecten_.

_Williamsonia indica_, sp. nov.

This name is proposed for some imperfect specimens described by

Feistmantel from the Godaveri district and named by him _Williamsonia_

sp. _cf._ _Williamsonia gigas_[1247]. They differ from _Williamsonia

gigas_ in the larger size of the bracts which reach a length of 13 cm.

and may be compared with those of a large specimen recorded from Mexico

as _Williamsonia Cuauhtemoc_[1248].

[Illustration: Fig. 558. _Williamsonia Blandfordi_ and _Ptilophyllum_

frond.

(Geological Survey of India; nat. size.)]

It is almost certain that some at least of the Indian flowers were

borne on stems with the foliage known as _Ptilophyllum acutifolium_, an

inference based not only on the almost constant association of flowers

and fronds but also on the juxtaposition of both kinds of organs with

stems precisely similar to those described from England and Mexico.

Though none of the specimens are sufficiently well preserved to afford

much information as to structural features, Miss Bancroft[1249] has

shown that the bracts of one of the examples assigned by Feistmantel

to _W. gigas_ are similar anatomically to those of _Williamsonia

scotica_ and are clothed with simple hairs. The important point is

the very close correspondence between the Indian and English types of

_Williamsonia_, as regards flowers, fronds, and stems.

+British Specimens.+

_Williamsonia Carruthersi_ Seward.

[Illustration: Fig. 559. _Williamsonia Carruthersi._ A, unexpanded

flower. A′, the reticulate lamellae projecting from the face of a

bract. B, the basal portion of a larger and expanded flower showing the

impressions of the interseminal scales and the base of the receptacle.

(British Museum, A, V. 3177; B, V. 3201.)]

This species was founded on several specimens from Wealden beds on

the Sussex coast none of which afford information as to anatomical

structure[1250]. It is not improbable that more than one species is

represented. The ovulate cone, 6 cm. long, is surrounded by several

linear bracts (fig. 559, A) and in shape resembles _Bennettites

Morierei_ Lign.; the bracts are broken across near the base, as is

frequently the case in _Williamsonia gigas_, exposing an annular zone

formed by persistent interseminal scales. From the inner face of some

of the bracts project slender radiating plates (fig. 559, A′) which

no doubt mark the boundary of the superficial and relatively large

interseminal scales, like those forming the so-called pericarp in

_Bennettites Gibsonianus_. The receptacle appears to have been conical,

a feature recalling _Bennettites_ rather than _Williamsonia_. The

saucer-like impression shown in fig. 559, B, is practically identical

with the corresponding portion of _Williamsonia Leckenbyi_: the centre

is occupied by a raised area, the basal part of the receptacle, on

which a series of peripheral prominences represents the vascular

strands; the sides of the saucer show very clearly the reticulum formed

by the distal ends of interseminal scales. One reason for assigning

this species to _Williamsonia_ rather than to _Bennettites_ (or

_Cycadeoidea_) is the occurrence in the same bed of a peduncle 12 cm.

long and 3 cm. broad which probably belonged to the parent-plant of

the cone. The surface of the peduncle shows spirally disposed scars of

bracts crowded at the distal end and more widely separated in the lower

portion.

_Williamsonia Bucklandi_ (Unger).

In 1837 Buckland[1251] gave an account of a ‘unique and beautiful

fossil fruit’ from Inferior Oolite beds at Charmouth in Dorsetshire

and stated that the type-specimen was in the Oxford Museum. Professor

Sollas kindly searched for the specimen some years ago but without

success. Buckland considered that the fruit was related to the

Pandanaceae and described it as follows: ‘The size of this fruit is

that of a large orange, its surface is occupied by a stellated covering

or epicarpium, composed of hexagonal tubercles, forming the summits

of cells, which occupy the entire circumference of the fruit. Within

each cell is contained a single seed, resembling a small grain of rice

more or less compressed, and usually hexagonal. When the epicarpium

is removed, the points of the seeds are seen, thickly studded over

the surface of the fruit. The bases of the cells are separated from

the receptacle by a congeries of foot-stalks formed of a dense mass

of fibres, resembling the fibres beneath the base of the seeds of the

modern _Pandanus_.’ At the suggestion of Robert Brown he called the

‘fruit’ _Podocarya_, the specific name _Bucklandi_ being afterwards

given by Unger[1252]. Brongniart[1253] called attention to the

resemblance of Buckland’s specimen to _Williamsonia_, and that name

has been adopted by Saporta[1254], Nathorst, and other authors[1255].

Sowerby’s drawings illustrating the original description, one of which

is reproduced in fig. 560, show that this unusually fine specimen is

an ovulate Bennettitean strobilus very similar in its thick conical

receptacle to some of Wieland’s species of _Cycadeoidea_, _e.g._ _C.

dacotensis_ (fig. 528): the armour of scales and megasporophylls agrees

exactly with that of some species of _Williamsonia_ from Yorkshire

and with the flowers of _Cycadeoidea_. Though included in the genus

_Williamsonia_ it would not be out of place in _Cycadeoidea_.

[Illustration: Fig. 560. _Williamsonia Bucklandi._ (After Buckland; ⅚

nat. size.)]

_Williamsonia scotica_ Seward.

The type-specimen was found by Hugh Miller near Cromarty (N.E.

Scotland) and figured as a cone of peculiar form[1256]; it was obtained

from a limestone nodule probably derived from Upper Jurassic rocks.

The fossil is 11 cm. long and has a maximum breadth of 6 cm. (fig.

561): numerous linear bracts cover the surface and in the lower portion

many of them are broken. A noteworthy feature is the absence of any

clean-cut base, a fact pointing to fracture rather than a natural

abscission of the fertile axis. The following description may serve

to give a general idea of the salient characters. Flowering shoot

ovoid, covered with linear bracts some of which are prolonged above

the conical apex as slender tapered organs and two of them bear a few

short lateral appendages (fig. 561, _l_), probably reduced leaflets,

near their distal ends. The cylindrical axis, completely hidden by

bracts, 1·5 cm. in its widest part, bears in the lower or sterile

region bracts and long hairs and in the upper part interseminal scales

and immature megasporophylls which together form a narrow band (fig.

562, _S_) 2 mm. broad extending over the incompletely preserved and

conical apex, as in some of the American examples of _Cycadeoidea_.

The strobilus was probably borne at the apex of a lateral branch given

off from a stem covered with persistent petiole-bases: there is no

evidence that this was the case, but the appearance of the ovoid cone

suggests comparison with those of _Williamsonia gigas_ which were

terminal on fairly long branches and not partially hidden among the

bases of fronds as in _Cycadeoidea_. It is, however, possible that the

cone of _Williamsonia scotica_ is a lateral structure: this suggestion

is based on the occurrence of a small branch or bud, which may be the

apex of the whole fertile shoot, given off from the cone-axis but only

revealed in transverse sections. The interseminal scales, 2 mm. long

and 0·23 mm. broad at the truncate distal end (fig. 563), are polygonal

in section and arranged as rosettes of 5–6 around each megasporophyll

(fig. 564, a section tangential to the peripheral layer of scales and

sporophylls). The megasporophylls, equal in length to the scales,

consist of a cylindrical axis bearing a terminal megasporangium, an

undifferentiated nucellus, enclosed in a single integument prolonged

as a micropylar tube above the conical end of the nucellus (fig. 563,

B, C, _a_). Fig. 562 represents a transverse section through the cone

showing the cylindrical axis with its compact covering layer (fig. 563,

A, _s_) of sterile and fertile appendages, and beyond this sections

of the enveloping bracts embedded in a dense felt of long hairs. The

tissue of the axis, though very imperfectly preserved, shows occasional

groups of secretory sacs and a few patches of scalariform tracheids:

there is evidence of the occurrence of peripheral conducting tissue

in the lower portion of the axis such as occurs in the peduncles of

American species of _Cycadeoidea_ described by Wieland. The bracts

nearer the axis are more shrivelled than those farther away, the

result of the feebler development of hypodermal stereome in the more

internal bracts. Sunken stomata occur on the lower surface of some of

the bracts: several collateral bundles are present in each and large

secretory ducts are abundant. The numerous hairs on the bracts and the

sterile region of the cone are outgrowths of epidermal cells; most of

them consist of a short basal cell and a very long thick-walled tubular

hair reaching a length of several centimetres. In some cases the basal

cell bears a group of short cells each of which is the starting-point

of a long hair: this is worthy of notice from the point of view of

comparison with the ramenta of other Bennettitalean flowers. The short

proximal cell of a hair is surrounded by a cuticular ring like a

rounded base-moulding where it rests on the epidermis: this has been

aptly compared to the dark rings that form a striking feature of the

cuticular membrane of _Ptilophyllum_ leaflets[1257].

[Illustration: Fig. 561. _Williamsonia scotica._ Strobilus in

surface-view; _l_, bract with short lateral appendages. (Royal Scottish

Museum, Edinburgh; ¾ nat. size.)]

[Illustration: Fig. 562. _Williamsonia scotica._ Transverse

section; _S_, scales and megasporophylls; _a_, bract showing detached

superficial tissue on the inner side. (_ca._ × 2.)]

[Illustration: Fig. 563. _Williamsonia scotica._ Megasporophylls

and interseminal scales in longitudinal section. A, part of the axis

showing the attachment, _s_, of a scale and megasporophyll. B, apex of

micropylar tube showing funnel-shaped cavity and papillose epidermal

cells on the integument and on the adjacent scale; _a_, apex of

nucellus. C, upper part of a scale and megasporophyll; _a_, apex of

nucellus. (A, _ca._ × 20; B, C, × 100.)]

[Illustration: Fig. 564. _Williamsonia scotica._ Transverse section

near the distal end of a micropylar tube and the surrounding polygonal

interseminal scales. (_ca._ × 100.)]

In the examination of the type-specimen the first section cut was

transverse to the axis (fig. 562), and this happened to traverse the

lowest part of the fertile region of the receptacle, as was shown by

the fact that in the next lower section the axis bore only bracts

and hairs. It is clear that the sterile portion of the receptacle

passed abruptly upwards into the fertile region, and it is extremely

unlikely that any microsporophylls were borne at the base of that

portion of the cone-axis which produced the scales and megasporophylls.

The cone was, in all probability, unisexual. On the analogy of the

cones shown in figs. 513, 514, one would expect to find between the

sterile and fertile regions either a verticil of microsporophylls or

the remains of an annular disc from which the effete sporophylls had

been detached. There is no trace of any such disc, and the fact of

the immaturity of the megasporophylls renders it unlikely that were

the cone bisexual the microsporophylls would have been detached. As

previous records show, there is nothing improbable in the occurrence

of a unisexual Bennettitean flower. These remarks are made in view

of an opinion expressed by Dr Wieland that the bracts with lateral

appendages (fig. 561, _l_), to which allusion has been made, are

microsporophylls and that if the cone had been sliced longitudinally

the presence of a microsporophyll-disc would have been discovered.

The latter possibility has already been considered, and as regards

the former there is nothing in the structure of the small lateral

appendages of the longest bracts to indicate that they were connected

with spore-production. It is not unlikely that the bracts with small

outgrowths (fig. 561, _l_) correspond to the more leaf-like bracts of

_Wielandiella_ and _Williamsoniella_. The two sets of organs spoken of

as interseminal scales and megasporophylls are probably homologous,

foliar, structures; in the one case leaves transformed into cylindrical

organs bearing terminal integumented and undifferentiated megasporangia

and, in the other, sterile or sterilised sporophylls. The polygonal

truncate distal end of an interseminal scale is flat or slightly

concave and covered by a thick epidermis, and on the sides of the

scale many of the surface-cells are strongly papillose (figs. 563,

564). The rest of the interseminal scale consists mainly of elongated

cells, which in the lower portion of the axis of the scale assume a

tubular form, presumably immature conducting elements: in one scale

only was any tracheal tissue found and that was represented by 2–3

scalariform tracheids. The scales appear to arise from the axis like

the bracts as superficial outgrowths, and probably in a later stage of

development the centre of each scale would be occupied by a vascular

strand. The megasporophylls bear a close resemblance to the scales,

but in transverse section they appear as smaller and circular organs

each the centre of a group of polygonal interseminal scales precisely

as in other Bennettitean flowers (fig. 564; _cf._ fig. 515). The

proximal part of a megasporophyll consists of a column of parenchyma

(fig. 563, A, _s_) extending through half of the length; from this

column is detached a narrow cylinder of small crushed cells which

most likely represents the remains of tissue that originally occupied

the space surrounding the axial column. At a higher level the axial

column becomes broader and its short cells more elongated and slightly

divergent towards the sloping sides of the conical nucellus. The loose

cylinder of tissue is attached to the nucellar cone and prolonged

beyond its apex as a broad integument enclosing a very small micropyle

(fig. 563, C). The apex of the integument has the form of a shallow

funnel: its epidermal cells are papillose (fig. 563, B, C) and the

presence of short transversely elongated cells is a characteristic

feature of the tissue lining the micropylar canal. The bracts agree

generally with those of _Cycadeoidea Gibsoniana_, _Cycadeoidea

Morierei_, and the American species. The ground tissue is composed of

sclerenchyma comparable with the scalariform elements in the bracts

of _Cycadeoidea Gibsoniana_ (_cf._ fig. 520). It is in the possession

of long hairs like those on the leaves of _Dioon_ and other recent

Cycads that _Williamsonia scotica_ differs from previously described

flowers in all of which the fern-like ramental scales are a conspicuous

feature. It is interesting to find that similar hairs are substituted

for scales in some Indian stems described by Miss Bancroft[1258].

Lignier[1259] mentions the occurrence of long unicellular hairs on

_Cycadeoidea micromyela_ (p. 415), a Jurassic French species, but

the ramenta are in part multicellular lamellae and the presence of

transitional forms suggests a possible derivation of hairs from scales

both in fossil species and in recent Cycads. The megasporophylls and

interseminal scales are much shorter than in _Cycadeoidea Gibsoniana_

and other species in which the axis of the cone forms a depressed

receptacle (_cf._ fig. 521, A, C), but they correspond closely with

those of several American species. In _Cycadeoidea Gibsoniana_ and _C.

Morierei_ the distal ends of the interseminal scales are much broader

and their diameter greatly exceeds that of the micropylar tubes, 2·8

mm. as compared with 0·25 mm., whereas in _Williamsonia scotica_

the scales are 0·23 mm. broad and the micropylar tubes 0·15 mm. The

mummified micropylar tubes of _W. pecten_ bear a striking resemblance

in form and in the papillose epidermal cells to those of the Scotch

species.

There are two additional points suggested by the structure of the

fertile region, namely the possibility that the megasporophylls are

arrested rather than immature organs and, secondly, the method of

pollination. In regard to the first there would seem to be no adequate

reason for doubting the correctness of the view that the sporophylls

are potentially perfect ovules which were petrified at a comparatively

early stage in development. The dense woolly covering investing the

surface of the scales and megasporophylls recalls an inflorescence

of _Aesculus hippocastanum_ in its winter-fur and hardly suggests a

collection of ovules accessible to microspores. In all probability at a

later stage the protecting bracts with their felt of hairs would bend

outwards leaving exposed the receptive micropyles.

+Microsporophylls.+

In view of the association of microsporophylls and ovulate strobili

in the flowers of _Cycadeoidea_ described by Wieland, most of which

are bisexual, it is reasonable to expect a similar association in the

flowers of _Williamsonia_ which agree closely in the essential features

of both micro- and mega-sporophylls with those of _Cycadeoidea_. It is,

therefore, surprising that in no single case have the microsporophylls

attributed to _Williamsonia_ been found in actual connexion with a

receptacle bearing interseminal scales and megasporophylls. The same

statement holds good with regard to the Williamsonias discovered

in Mexico. Nathorst believes that the microsporophylls on which he

has founded several species are unisexual flowers with the possible

exception of _W. pyramidalis_[1260]. This species, found by Dr Halle

at Cloughton Wyke, is represented by a small ovulate strobilus

characterised by a conical receptacle with a blunt mucronate apex: with

it is associated a microsporophyll bearing synangia. The orientation

of the two specimens is such as to suggest an original connexion.

As Nathorst says, there is, however, no proof that the two belong

to one flower. Wieland[1261], though believing that the existence

of bisporangiate Williamsonia flowers is ‘reasonably certain,’

agrees with Nathorst’s conclusion as to the unisexual character of

_W. spectabilis_ and _W. pecten_. On the other hand, he regards the

microsporophyll-verticil which was first described by Williamson as

a carpellary disc, then named by Nathorst[1262] _W. bituberculata_

and afterwards identified as a microsporophyll-disc closely allied

to _W. whitbiensis_, as the staminate part of _W. gigas_. This view

is, in my opinion, impossible to reconcile with the nature of the

specimen. If, as Wieland suggests, it is the staminal collar split

off from the base of a large ovulate cone like that of _Williamsonia

gigas_, one would expect to find a central space in the middle of the

cupular base large enough to embrace the receptacle. Neither in this

specimen nor in several other forms of microsporophyll-verticils is

there such a central space. It is clear that the discs described as

_W. spectabilis_, _W. whitbiensis_, and other species were not borne

as concrescent collars on a stout axis as are the corresponding organs

in _Cycadeoidea_. The Indian specimen reproduced in fig. 557 and the

very closely allied type _W. setosa_ are incomplete at the centre and

may possibly have been borne at the base of an ovulate bisporangiate

strobilus, but there is no definite evidence that this was the case.

Moreover, in _W. spectabilis_ the lower part of the cup (fig. 551)

easily splits away from the rest of the staminate disc, and this may

explain the central space in the specimen shown in fig. 549, A. If _W.

spectabilis_, to take one example, is a complete flower there are

certain difficulties which are not easily explained: as Nathorst has

shown, in this type there is a short stalk, but in _W. whitbiensis_

the base of the funnel has no stalk and there is no interruption of

the stout lamina at the centre or any indication of a scar. Nathorst

compares the funnel-like region of _W. whitbiensis_ to a kind of

cupule which became detached after flowering[1263]. But a cupule is

supported on an axis and, though no scar is apparent on some of the

more complete specimens, it is obvious that the verticil must have been

supplied with vascular tissue from some axial organ. This brings us to

the consideration of a morphological point which cannot be definitely

answered. Nathorst has previously raised the question—is it possible

that the microsporophylls were attached to the upper part of an ovulate

strobilus; were the flowers bisexual and epigynous? He believes the

answer to be in the negative. Reference has already been made to the

probable occurrence at the apex of the receptacle of _Williamsonia

gigas_ of a funnel-like organ of the type described by Williamson as

‘carpellary disc[1264],’ a term under which Nathorst[1265] believes

that Williamson included two different things,—staminate discs

borne on separate, unisexual, flowers, and sterile organs called

by Lignier[1266] the infundibuliform apparatus. The latter, it is

believed, were attached to the apex of an ovulate strobilus as shown

in fig. 548, comparable in position with the leaves at the summit of

an inflorescence of _Ananas_. A comparison of the fossils regarded as

infundibuliform appendages with some of the microsporophyll-verticils

shows that they are identical in form, the only difference being

that on the former there are no synangia. This fact can hardly be

regarded as negative evidence fatal to the morphological identity of

these sterile and fertile organs. The available evidence, though far

from complete, is favourable to the view that in some _Williamsonia_

flowers, _e.g._ _W. gigas_, the microsporophylls were produced at the

apex of the axis in the position shown in fig. 548. To cite a rough

analogy,—in _Cycadeoidea_ the flower was hypogynous as in _Erica_; in

_Williamsonia_ epigynous as in _Vaccinium_. This view does not exclude

the possibility of the existence of unisexual flowers in some species,

but the evidence in favour of a separation of the sexes is by no means

decisive. Another difficulty is the absence of protective bracts in the

case of the microsporophylls, a striking contrast to the bract-enclosed

ovulate strobili of _Williamsonia_ or to the bract-covered flowers

of _Cycadeoidea_. Were the microsporophylls borne on a separate axis

general considerations would lead us to expect the association of

bracts with the essential organs. The fact that no such association has

been recorded is a fact favourable to the view that the flowers were

bisporangiate.

[Illustration: Fig. 565. A, _Williamsonia spectabilis_,

microsporophyll; B, _W. whitbiensis_, section of sporophyll; C, _W.

mexicana_. (A, B, after Nathorst; C, after Wieland.)]

The student is warned that the opinion expressed with regard to the

position of the microsporophylls is contrary to that which is held by

several palaeobotanists[1267].

_Williamsonia mexicana_ Wieland.

This species is one of the numerous types discovered by Wieland in

Mexico[1268]. It is distinguished by the deep campanulate concrescent

portion of the whorl of microsporophylls and by the ten short free

lobes which bear two rows of lateral synangia (fig. 565, C). Among

the British forms _Williamsonia whitbiensis_ would appear to be the

most closely allied type. _W. mexicana_ occurs in association with

_Otozamites_ fronds, as is the case with an Italian specimen figured by

Zigno[1269], but in the Mexican species there is no conclusive evidence

of organic connexion.

+Other species of Williamsonia.+

_Williamsonia Haydeni_ Seward.

A Jurassic species from Afghanistan[1270] founded on a single specimen

of a flattened broadly-oval flower similar to _W. gigas_ but smaller

and enclosed by narrow linear bracts. An interesting feature is the

occurrence of a funnel-shaped depression at the apex showing radiating

lines on its surface as in the _Williamsonia_ represented in fig. 546,

A. In all probability these lines denote the persistence of a collar

of interseminal scales on the upper part of the elongated conical

receptacle. An examination of the carbonaceous material revealed

the presence of some short rods agreeing in size and shape with the

interseminal scales of other species.

_Williamsonia Otozamitis_ (Zigno).

Zigno[1271] instituted the generic name _Blastolepis_ for some

specimens from the Jurassic rocks of north Italy which he referred to

three species, _B. falcata_, _B. acuminata_, and _B. Otozamitis_. These

are true Williamsonias closely allied to _W. gigas_. An examination of

the type-specimen of _B. Otozamitis_ in the Padua collection led me

to the conclusion that Zigno was correct in representing the ovulate

strobilus, which shows an annular area like that in specimens of _W.

gigas_, as being in organic connexion with an _Otozamites_ frond.

Wieland has recently discovered species of _Williamsonia_ in Mexico

that he correlates with _Otozamites_ leaves.

_Williamsonia_ sp. Seward.

Though by no means satisfactory as a trustworthy record of the genus,

the specimens so designated from the Kimmeridgian of Scotland[1272] are

probably imperfect examples of the genus.

_Williamsonia oregonensis_ Fontaine.

The type-specimen from Jurassic rocks in Oregon[1273] consists of a

stout axis bearing several contiguous linear bracts forming a more or

less spherical cluster 5 cm. broad. The form suggests a _Williamsonia_,

but the evidence is hardly decisive.

_Williamsonia Forchammeri_ Nathorst.

A Bornholm species[1274] from Lower Jurassic strata represented by

an annular zone surrounding a central area, probably a portion of an

ovulate strobilus.

_Williamsonia minima_ Saporta.

This Upper Jurassic species from Portugal[1275] consists of a number of

small bracts or leaves attached to a central axis and is of no value as

evidence of the occurrence of _Williamsonia_.

_Williamsonia problematica_ (Newberry).

This species was first described from the Amboy clays as _Palaeanthus_

(_Williamsonia_) _problematica_[1276] and compared to a Composite

inflorescence with long ray-florets. More recently Hollick[1277] has

referred to this species specimens from the Cretaceous of Long Island

and Martha’s Vineyard, but none of them afford conclusive evidence of

Williamsonian affinity. Some of the examples, as suggested by Hollick,

agree fairly closely with _Williamsonia cretacea_ Heer.

_Williamsonia Smockii_ Newberry.

The curious urn-like bodies from the Amboy clays[1278] on which this

species is based are not unlike the capsules of a _Papaver_ but bear no

real resemblance to a _Williamsonia_.

_Williamsonia Riesii_ Hollick.

A species from the Cretaceous rocks of Martha’s Vineyard[1279] referred

to _Williamsonia_ on rather slender grounds and represented by

imperfect material.

_Williamsonia_ (?) _phoenicopsoides_ Ward.

This fossil from the Cretaceous of the Black Hills, Dakota[1280], is

much too imperfect to be accepted as a record of _Williamsonia_.

_Williamsonia elongata_ Lesquereux.

This species, founded on part of a conical receptacle with some

appendages superficially resembling those of _Williamsonia_[1281], is

too incomplete to be determined with any confidence. The type-specimen

is from Cenomanian beds in Kansas.

_Williamsonia virginiensis_ Fontaine.

This is undoubtedly a true member of the genus; it is characterised by

narrow ovate bracts bearing conspicuous hairs surrounding the base of

a receptacle which shows a portion of an annular zone of interseminal

scales[1282].

_Williamsonia_ (?) _gallinacea_ Ward.

This species from the Potomac beds[1283] is of no value as a record of

_Williamsonia_.

_Williamsonia_ (?) _Bibbinsi_ Ward.

The imperfectly preserved specimen from the Potomac series so named

by Ward[1284] is probably part of an Abietineous cone as stated by

Berry[1285] who includes Ward’s type with other specimens referred to

_Abietites macrocarpus_ Font.

_Williamsonia cretacea_ Heer.

Two specimens, figured by Heer[1286] from the Lower Cretaceous of

Greenland, on which this species is founded, consist of an axis covered

with small scale-leaves and at the broad apex bearing numerous narrow

linear bracts forming a more or less spherical cluster 3·8 cm. in

breadth. The species resembles _W. problematica_ (Newb.).

_Williamsonia recentior_ Dawson.

The specimens from the Middle Cretaceous of Canada figured by

Dawson[1287] under this name are very imperfect and of no botanical

value.

[Illustration: Fig. 566. _Wielandiella angustifolia._ (After

Nathorst.)]

=WIELANDIELLA.= Nathorst.

The specimens on which this genus is founded were originally described

by Nathorst from Höör in Scania as _Williamsonia angustifolia_[1288]:

in a second paper[1289] a restoration of the plant was published (fig.

566). The examination of additional specimens from the Rhaetic of

Bjuf and of cuticular preparations led to the establishment of a new

genus _Wielandia_[1290] for which _Wielandiella_[1291] was afterwards

substituted, _Wielandia_ having been previously employed for an

existing plant. _Wielandiella_ agrees in the general morphology of

its bisporangiate flowers with _Cycadeoidea_, but differs widely from

nearly all other members of the Bennettitales in the repeatedly forked

slender stem which is in marked contrast to the vegetative axis of any

recent Cycad. Among recent Cycads with terminal strobili an indication

of a primitive dichasium is afforded by the occurrence of an aborted

bud in a stem of _Dioon edule_ described by South and Compton[1292];

but in the habit of the stem _Wielandiella_ is far removed from any

recent Cycadean type. The microsporophylls are smaller and simpler than

in _Williamsonia_ or _Cycadeoidea_ and the foliage-leaves are of the

_Anomozamites_ type (_cf._ fig. 615).

[Illustration: Fig. 567. _Wielandiella angustifolia._ Branched stem

and receptacle. (After Nathorst.)]

_Wielandiella angustifolia_ Nathorst.

In an account of this species in 1902 Nathorst described two types of

strobilus, male and female, but a re-investigation of the material led

to a modification of the earlier conclusions. The stem is slender,

rarely exceeding 1·5 cm. in breadth, repeatedly branched as a dichasial

system with a fertile shoot in the forks formed by the equal and

widely divergent branches. Nathorst’s restoration, as he points out,

may exaggerate the regularity of the branching, but an examination of

the original specimens in the Stockholm Museum convinced me that the

habit represented in fig. 566 is substantially correct. The method of

branching is similar to that in the inflorescences of Gnetalean plants

and recalls some _Gleichenia_ fronds. The surface of the thicker pieces

of stem shows fine longitudinal striae, while transverse striations

like those on the axis of a _Heterangium_ frond characterise the

more slender specimens. Closely set polygonal leaf-scars cover the

stem for a short distance below each bifurcation and the surface of

the short and relatively stout peduncles of the strobili (fig. 567).

Though for the most part confined to the region of false dichotomy,

leaf-scars occasionally occur on other parts of the stem. Small

fronds, 7–8 cm. long, agreeing closely with _Anomozamites minor_

Brongn., occur in the same beds at Bjuf, and the striking resemblance

between their long linear and winged petioles and the transversely

striated bracts enclosing the strobili of _Wielandiella_ amply

justifies Nathorst’s conclusion that _Wielandiella_ bore fronds of the

_Anomozamites_ form[1293]. Small scars marking the position of bracts

occur immediately below each strobilus and occasionally form narrow

zones between the larger foliage leaf-scars. The strobili are met with

in two forms representing two states of preservation and, probably,

different ages. In one form the strobilus consists of a small pyriform

axis separated from the peduncle by an annular swelling characterised

by parallel striations (fig. 567), the so-called palisade-ring. From

this ring Nathorst obtained many microspores scattered and in groups

on the surface of short sporophylls, 2·5–3 mm. in length. It is these

sporophylls which form the parallel striations; they occur as a circle

of rather broad linear organs with irregularly toothed distal ends and

an epidermis of papillose cells. The oval microspores, 32–42μ long,

vary in size and, as Nathorst says, this may indicate immaturity. The

precise mode of occurrence of the spores has not been ascertained, but

they were probably produced in sporangia on the surface of the small

microsporophylls. These strobili have in all probability lost the

female organs which were borne on the pyriform axis, and the inference

is that the strobili were protogynous. Thomas[1294] compares the ring

at the base of the flower-axis from which spores were obtained by

Nathorst to the whorl of microsporophylls of _Williamsoniella_, but

in _Wielandiella_ the sporophylls are greatly reduced and possibly

functionless. _Wielandiella_ may be intermediate between the bisexual

_Williamsoniella_ and the unisexual _Williamsonia scotica_. In the

second form of strobilus the pyriform axis is hidden and the specimens

consist of a central ovate body, approximately 3 cm. long, surrounded

by several linear bracts (fig. 568, A). The carbonised surface of the

central region revealed on chemical treatment a fairly regular pattern

formed by the contiguous polygonal ends of interseminal scales arranged

round smaller cylindrical micropylar tubes which project beyond the

level of the scales (fig. 568, B). This arrangement agrees closely with

that of the corresponding organs in _Williamsonia_ and _Cycadeoidea_

(_cf._ figs. 515, 564). In _Wielandiella_ the micropylar tubes are of

uniform diameter and the cells of the epidermis have smooth walls in

contrast to the micropylar tubes of _Williamsonia_ (fig. 563). The

strobilus in this state, before the scales and ovules have become

detached from the axis, may be described as a small _Williamsonia_, but

the habit of the stem is in itself a sufficient reason for the use of a

distinctive generic name[1295].

[Illustration: Fig. 568. _Wielandiella angustifolia._ A, conical

receptacle with bracts. B, surface-view of scales and micropylar tubes.

(After Nathorst; A, ¾ nat. size.)]

A second species, _Wielandiella punctata_, described by Nathorst[1296]

from Scania is founded on pieces of forked stems associated

with fragments of a palisade-ring formed of contiguous segments

(microsporophylls) with microspores 58μ in length. Fronds of

_Anomozamites minor_ occur in the same beds.

Mr Hamshaw Thomas[1297] described some specimens from the Middle

Jurassic beds of Marske in Yorkshire which he suggested might be pieces

of a _Wielandiella_ stem. Additional material was subsequently found

and this enabled Thomas to produce evidence in favour of connecting the

branched vegetative axis with bisporangiate strobili and the fronds of

_Taeniopteris vittata_. For the stems and flowers the new designation

_Williamsoniella_ has been proposed. Further research will no doubt

show that the _Wielandiella_ type of stem was not exceptional in

Rhaetic and Jurassic floras.

Nathorst[1298] suggests the possibility that some specimens from the

Solenhofen Slates described by Thiselton-Dyer[1299] as _Condylites

squamatus_ may be allied to _Wielandiella_. The generic name

_Condylites_ was suggested by the elbow-like branching of stems which

bore imperfectly preserved and apparently terminal cones; the surface

of the branches is covered with the scars of leaves. The resemblance to

_Wielandiella_ is, however, slight and it would seem more probable that

the Solenhofen fossils are Coniferous, though, as Nathorst says, the

supposed scale-like ‘leaves’ may be scars of Cycadean fronds.

Wieland[1300] records the occurrence in Mexico of stems similar to

those of _Wielandiella_ associated with some _Otozamites_ fronds.

=WILLIAMSONIELLA.= Thomas.

This genus was instituted for specimens discovered by Mr Hamshaw

Thomas[1301] in the Middle Estuarine series of the Middle Jurassic

plant-bed at Gristhorpe on the Yorkshire coast, and the genus is

recorded also from the Cleveland district in the same county.

_Williamsoniella_ occurs in those parts of the Gristhorpe bed where

fronds of _Taeniopteris vittata_ are abundant.

_Williamsoniella coronata_ Thomas.

The type-species is represented by fertile shoots consisting of a

central axis bearing both megasporophylls and microsporophylls (figs.

569, 571, A). Below its crown-like sterile apex the pyriform peduncle

is covered with small interseminal scales and ovules similar to those

of _Williamsonia_: this portion is 6 mm. in diameter and 1 cm. long.

A whorl of separate cuneate microsporophylls forms a hypogynous ring

below the basal interseminal scales: each sporophyll is attached by

a narrow base (fig. 570) and bears 5–6 reniform synangia containing

microspores. The flower is thus bisexual: it affords no conclusive

evidence of the occurrence of any covering bracts like those of most

Bennettitalean flowers. In young specimens the microsporophylls are

closely packed round the axis (fig. 571, B). The flower-stalks reach

a length of 3·5 cm. and are 3 mm. in diameter. Fig. 571, C, shows a

receptacle from which the sporophylls have fallen: the microsporophylls

having been no doubt attached to the collar-like swelling at the base.

Towards the apex the axis becomes broader and at _s_ a few interseminal

scales are left: above these is the apical disc (corona) characterised

by longitudinal ribs. An apical disc is reproduced in fig. 572; it

has the form of a royal crown 1–2 mm. high with 12–16 vertical ridges

separating flat surfaces formed by the pressure of microsporophyll

apices in the unexpanded flower. The corona is surmounted by a small

conical elevation which represents the apex of the fertile axis. An

apical view of an unexpanded flower is shown in fig. 571, B; the

tips of 12 sporophylls are closely pressed against the corona which

probably consists in part at least of fused interseminal scales. The

microsporophylls were shed after the dehiscence of the synangia. Each

sporophyll is flattened on the sides and thicker on the curved outer

edge; the synangia, usually in two rows of three, are borne on the

sloping sides (figs. 569, 570). The surface of a microsporophyll is

covered with small rounded projections which produce a characteristic

appearance. The form of a microsporophyll in section is shown in fig.

570: the synangia are similar in shape to those of _Cycadeoidea_ and

_Williamsonia_ (_cf._ figs. 531, 549, etc.) but there are no external

indications of septa like those seen in some other types. On macerating

some specimens it was found that the spores occur in about 20 groups.

The circular or elliptical spores are 0·02 mm. in diameter. The walls

of the epidermal cells of the microsporophylls are straight: the

stomata, which show the features characteristic of the Bennettitales,

agree closely with those of _Taenopteris vittata_.

[Illustration: Fig. 569. _Williamsoniella coronata._ Vertical section

of the flower showing the pyriform axis with small megasporophylls and

interseminal scales and the microsporophylls with synangia. (After

Thomas; × 2.)]

[Illustration: Fig. 570. _Williamsoniella coronata._ Diagrammatic

sketch of a microsporophyll in section and in side-view. (After Thomas;

× 3.)]

[Illustration: Fig. 571. _Williamsoniella coronata._ A, flower

showing two microsporophylls and the central axis with megasporophylls.

B, apical view of an unexpanded flower. C, flower-axis showing the

shallow grooves made by the infolded microsporophylls, which have

fallen, and a few megasporophylls, _s._ (After Thomas; A, × 1⅓; B, C, ×

3.)]

[Illustration: Fig. 572. _Williamsoniella coronata._ Apical disc with

megasporophylls and interseminal scales at the base. (After Thomas; ×

3.)]

The interseminal scales associated with the ovules and covering the

pyriform axis above the microsporophylls are more or less flattened

and hexagonal and the micropylar tubes often project far beyond

the scales. Each micropyle-tube is surrounded by 5–6 interseminal

scales (_cf._ fig. 564). The ovules differ from those of _Cycadeoidea

Gibsoniana_ in the absence of a distinct pedicel and agree with the

corresponding organs of _Williamsonia scotica_[1302]. In the absence of

epidermal papillae the micropylar tubes resemble those of _Wielandiella

angustifolia_. As already stated, the flowers appear to be without

protective bracts, but in the shale from which the specimens were

obtained a few bract-like organs were discovered consisting of a

lanceolate lamina 1·5 cm. long, and 2–3 mm. broad near the base,

and some showed a small oval lamina at the apex with a midrib and

dichotomously branched lateral veins. These bracts with the terminal

lamina are regarded by Thomas as almost certainly reduced leaves of the

_Taeniopteris vittata_ type: they are represented in the restoration

(fig. 573) as occurring at the base of the flower-peduncle. Stomata

were found on the bracts exactly like those on the microsporophylls,

and this affords a strong argument in support of the view that

_Williamsoniella_ belongs to the plant which bore _Taeniopteris_

fronds. There is a close parallelism between the bracts accompanying

_Williamsoniella_ flowers and those described by Nathorst in connexion

with _Wielandiella_[1303]. It seems reasonable to regard the bracts as

serving the purpose of bud-scales.

[Illustration: Fig. 573. _Williamsoniella coronata._ Restoration

of part of a plant: the upper leaves are represented only by the

petiole-bases. (After Thomas; _ca._ ⅜ nat. size.)]

An important point is the constant association with the flowers of

_Taeniopteris vittata_ fronds, a species described in Vol. +ii.+ and by

most palaeobotanists regarded as a Fern frond. _Taeniopteris_ leaves

occasionally show a clean-cut base[1304] and in specimens described

by Thomas there are two small humps on the surface of the proximal

end of the petiole which represent vascular bundles. Humps of similar

size occur on the leaf-scars of stems which are believed to have borne

both _Taeniopteris_ leaves and _Williamsoniella_ flowers. Fragments

of the stems were found in association with flowers: they are 7 mm.–2

cm. in diameter and frequently forked and there is evidence that the

flowers were borne at the forks, the shoot forming a dichasial system.

The habit of the plant is represented in fig. 573 reproduced from Mr

Thomas’s paper.

_Williamsoniella Lignieri_ (Nathorst).

This species described by Nathorst as _Williamsonia_? _Lignieri_ from

Whitby is regarded by Thomas as a _Williamsoniella_. The stomata on

the microsporophylls agree with those of _Taeniopteris_ and the spores

obtained from Nathorst’s flower-buds are like those of _Williamsoniella

coronata_. Evidence is adduced by Thomas in favour of regarding _W.

Lignieri_ as bisexual and not unisexual as Nathorst supposed.

In habit _Williamsoniella_ resembles _Wielandiella_: in the latter

genus the foliage-leaves were confined to portions of the stem near

the forks, while in _Williamsoniella_ they were more uniformly

scattered: _Wielandiella_ bore leaves of the _Anomozamites_ form while

_Williamsoniella_ flowers are always associated with _Taeniopteris_

fronds. The much greater spore-output of _Williamsonia_ may, it is

suggested by Thomas, be correlated with the unisexual nature of the

flowers of that species. The microsporophylls of _Williamsoniella_

differ in their more reduced form from the pinnate microsporophylls of

_Williamsonia_, _e.g._ _W. spectabilis_, and agree more closely with

those of _Wielandiella_. The microsporophylls of _Williamsoniella_

are free and not connate at the base as in _Cycadeoidea_ and

_Williamsonia_. In its pyriform axis _Williamsoniella_ resembles

_Williamsonia gigas_ and differs from _Williamsonia Leckenbyi_ in

the possession of a sterile apical corona: _Williamsoniella_ has

megasporophylls and microsporophylls both of which appear to be

functional, while in _Cycadeoidea_ fully developed microsporophylls

occur in association with megasporophylls which are immature and must

have matured much later than the microsporophylls. The new genus

agrees with _Williamsonia_ in its general features, but the flowers

are smaller and are characterised by the considerable reduction and

simplification of the male organs.

=CYCADOCEPHALUS.= Nathorst.

This genus was founded[1305] on a specimen from the Lower Rhaetic

of Scania, at first regarded as a megastrobilus and on further

examination[1306] found to be a collection of microsporophylls

resembling those of _Williamsonia_ and _Cycadeoidea_. The type-species

is _Cycadocephalus Sewardi_, and a second species, _C. minor_, was

subsequently discovered by Dr Halle at a slightly higher horizon in

the Rhaetic series. Prof. Nathorst’s most recent account of the genus

affords a striking illustration of the possibilities of the method,

which he has employed with conspicuous success, of investigating

carbonised fossils by means of cuticular preparations.

[Illustration: Fig. 574. _Cycadocephalus Sewardi._ A, surface-view;

_a_, appendages. B, the same specimen, after the removal of some

of the microsporophylls, showing the appendages. C, section of a

microsporophyll showing the attachment of appendages. D, section of an

appendage. (After Nathorst. A, B, ¾ nat. size.)]

_Cycadocephalus Sewardi_ Nathorst.

The type-specimen consists of an oval cluster of 16–18 linear

microsporophylls, 9 cm. long, springing from a small circular disc

formed of their concrescent and narrow bases. The whole flower (fig.

574) exclusive of the peduncle is 10 cm. long and 7 cm. broad. The

portion of the comparatively slender peduncle that is preserved shows

no trace of leaf-scars. In the middle of each linear microsporophyll

is a keel-like midrib and on either side of this is a series of linear

appendages (fig. 574) 2–3 cm. long lying in a radial direction towards

the centre of the flower. These appendages were originally thought to

be seeds (fig. 574, _a_), but it was suggested by Wieland that they

might be synangia, the circle of leaves being the male portion of a

bisexual flower of the _Cycadeoidea_ type. Nathorst’s more complete

investigation of the specimen confirmed the first of these suggestions,

but there is no evidence that there was an ovulate receptacle in the

centre of the flower. The appendages are attached by a rather broad and

slightly cordate base and are represented by a thin carbonised cuticle

of rectangular cells showing in one case a row of imperfectly preserved

stomata: on this are numerous groups of tetrahedral microspores, about

55μ in diameter, which show a more or less well marked arrangement in

rows transverse to the long axis of the thin laminae. It is clear from

Nathorst’s researches that the groups were enclosed in loculi bounded

by thin-walled cells[1307], the loculi being in transverse rows on

each side of a midrib. Nathorst speaks of the appendages as synangia

characterised by the large number of the sporogenous compartments,

and he compares them especially to the fertile leaflets of _Danaea

elliptica_ as described by Bower[1308], each appendage being comparable

with a revolute _Danaea_ pinnule in which the edges of the lamina

are united. This is illustrated by the section of an appendage (fig.

574, D) reproduced from Nathorst’s restoration of a _Cycadocephalus_

microsporophyll. From a morphological point of view it would seem more

appropriate to speak of the appendages as highly modified pinnules

rather than synangia. The second species, _C. minor_, agrees closely

except in its smaller size with the type-species. Nathorst regards

_Cycadocephalus_ as a unisexual flower differing from those of

_Williamsonia_ and from the microsporophyll-verticils of _Cycadeoidea_

in the structure of the synangia and in the tetrahedral form of the

spores, though the latter feature he considers to be of secondary

importance, as both bilateral and radial spores occur in recent

Marattiaceae. He includes the genus in the Bennettitales but suggests

that it should be referred to a separate family as an indication of

the possession of characters which mark it off from _Williamsonia_,

_Weltrichia_, _Wielandiella_, and _Cycadeoidea_.

=WELTRICHIA.= Braun.

The name _Weltrichia_ was given by Braun[1309] to some Rhaetic fossils

discovered by Weltrich near Culmbach in Franconia which represent

funnel-shaped structures, the lower part having the form of an

incomplete cup made of the concrescent bases of about 20 broadly

linear segments which in the upper part are separate lanceolate

lobes each with a midrib and slightly curved inwards at the apex.

The whole, nearly 10 cm. long and 9 cm. in diameter at the upper

edge, is very similar to the specimen of _Williamsonia spectabilis_

reproduced in fig. 551. Braun described three species, but he realised

the possibility that the different forms may be different stages in

the development of a single type _Weltrichia mirabilis_. He assigned

the genus to the Rhinantheae. Saporta[1310] drew attention to the

resemblance of Braun’s species to some examples of _Williamsonia_ from

Yorkshire which he considered to be portions of a sterile appendage

borne at the apex of the flower. Some account is given of two types

of funnel-like structures connected with _Williamsonia_ flowers on a

previous page[1311]: one of these has been shown by Nathorst to be

a whorl of microsporophylls, and it is with this that _Weltrichia_

agrees. An important feature of _Weltrichia_ is the occurrence of short

linear segments, 5–8 mm. long, attached to the inner face of each of

the free portions of the linear lobes: the lobes, or more correctly

the free apical portions of the fertile leaves, and their slender

appendages are compared by Nathorst[1312] to the microsporophylls and

relatively long synangia-bearing appendages of _Cycadocephalus_. These,

presumably fertile, segments of _Weltrichia_ project in the flattened

impressions beyond the edges of the free lobes of the campanulate

flower and look like marginal teeth, though they are actually

attached on each side of the midrib and originally extended, as in

_Cycadocephalus_, towards the centre of the funnel-shaped flower. The

examination of one of the type-specimens acquired by Nathorst[1313] for

the Stockholm Museum enabled him to confirm his earlier conclusion that

_Weltrichia_ represents the male portion of a flower, whether unisexual

or bisexual cannot be definitely determined, of a Bennettitalean

plant. There is, as Nathorst states, a close agreement in plan between

_Weltrichia_, _Cycadocephalus_, and _Williamsonia_, and indeed it is

not clear in what respects _Weltrichia_ is sufficiently distinct from

_Cycadocephalus_ to be retained as a separate genus. Our knowledge

of _Weltrichia_ is, however, less complete than in the case of

_Cycadocephalus_ and _Williamsonia_. It is noteworthy that Braun’s

specimens and those on which _Cycadocephalus_ was founded were obtained

from Rhaetic rocks. An account of _Weltrichia_ has also been published

by Schuster[1314] who differs from Nathorst in his interpretation of

the type-specimens: he considers that another fossil described by

Braun and named by him _Palaeoxyris microrhombea_ is the central,

female, portion of a _Weltrichia_ flower, a view that is not supported

by any substantial evidence. The specimens referred by Braun to

_Palaeoxyris_ and afterwards transferred by Schimper[1315] to the genus

_Lepidanthium_ are too obscurely preserved to be determined with any

degree of confidence, and their connexion with _Weltrichia_ is purely

hypothetical. With _Weltrichia_ Schuster also connects the fronds

known as _Otozamites brevifolius_ Braun and some impressions of stems,

combining all in a restoration of a complete _Weltrichia_ plant which

rests more on imagination than on fact. Attention has elsewhere[1316]

been called to some wholly misleading and incorrect statements made by

Schuster which vitiate the value of his descriptions.

Saporta[1317] described a species of _Weltrichia_, _W. Fabrei_. from

French Rhaetic strata at Mende (Lozère) which bears at least a close

superficial resemblance to _Williamsonia spectabilis_, and the same

author founded another species, _Weltrichia oolithica_, on a drawing by

Zigno of a specimen from Jurassic rocks in Italy; but this appears to

be too imperfect for accurate identification.

All that can be said as to the nature of _Weltrichia_, as illustrated

by the type-species, is that it represents a Rhaetic example of a

verticil of microsporophylls very similar to those of _Williamsonia_

and _Cycadocephalus_, if not generically identical with the latter form.