CHAPTER XXXVII.. Bennettitales (_continued_).

BENNETTITALES (continued).

=WILLIAMSONIA.= Carruthers.

This genus was first figured by Young and Bird 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 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 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 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 who was the first to attempt an exhaustive account of the genus, and the other by Carruthers 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, 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 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 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 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 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; 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. The stem reproduced in fig. 541, about 5 cm. broad, is imperfectly preserved and the leaf-bases are not clearly seen. Saporta’s figure 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 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 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.

In a former account of this species 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 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.

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 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.

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, Nathorst, and Krasser 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).

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 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 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 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.

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. 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, 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.

Williamsonia gigas (Microsporophylls).

In the course of an examination of the Williamsonia specimens (from Yorkshire) in Paris in July of last year (1914) Mr Thomas 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, 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. 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, 58–65µ in length, are rather narrow, ovate and very similar to those described by Solms-Laubach 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), and it is not unlikely that some of the impressions described as infundibuliform appendages are incomplete examples of Williamsonia spectabilis.

(Restoration after Nathorst.)]

Williamsonia Leckenbyi Nathorst.

This species, founded on specimens from the Middle Estuarine beds exposed on the Yorkshire coast at Cloughton Wyke, 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, 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 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. 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 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.

(After Nathorst.)]

Williamsonia whitbiensis Nathorst.

Under this name Nathorst 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 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.

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’: 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, 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 (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, 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, bears a striking resemblance to an Indian fossil described by Feistmantel from India.

+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 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 refigured this specimen and referred it to Williamsonia gigas though on insufficient grounds. To the same species Feistmantel 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.

A third example from the same locality (fig. 557) is described by Feistmantel as part of one of Williamson’s ‘carpellary discs,’ 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 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, 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. 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, 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. 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.

(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 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.

This species was founded on several specimens from Wealden beds on the Sussex coast none of which afford information as to anatomical structure. 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 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. Brongniart called attention to the resemblance of Buckland’s specimen to Williamsonia, and that name has been adopted by Saporta, Nathorst, and other authors. 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.

Williamsonia scotica Seward.

The type-specimen was found by Hugh Miller near Cromarty (N.E. Scotland) and figured as a cone of peculiar form; 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.

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. Lignier 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. 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, 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 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. 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,’ a term under which Nathorst believes that Williamson included two different things,—staminate discs borne on separate, unisexual, flowers, and sterile organs called by Lignier 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.

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.

Williamsonia mexicana Wieland.

This species is one of the numerous types discovered by Wieland in Mexico. 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, 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 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 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 are probably imperfect examples of the genus.

Williamsonia oregonensis Fontaine.

The type-specimen from Jurassic rocks in Oregon 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 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 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 and compared to a Composite inflorescence with long ray-florets. More recently Hollick 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 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 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, 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, 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.

Williamsonia (?) gallinacea Ward.

This species from the Potomac beds is of no value as a record of Williamsonia.

Williamsonia (?) Bibbinsi Ward.

The imperfectly preserved specimen from the Potomac series so named by Ward is probably part of an Abietineous cone as stated by Berry who includes Ward’s type with other specimens referred to Abietites macrocarpus Font.

Williamsonia cretacea Heer.

Two specimens, figured by Heer 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 under this name are very imperfect and of no botanical value.

=WIELANDIELLA.= Nathorst.

The specimens on which this genus is founded were originally described by Nathorst from Höör in Scania as Williamsonia angustifolia: in a second paper 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 for which Wielandiella 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; 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).

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. 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 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.

A second species, Wielandiella punctata, described by Nathorst 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 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 suggests the possibility that some specimens from the Solenhofen Slates described by Thiselton-Dyer 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 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 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.

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. 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. It seems reasonable to regard the bracts as serving the purpose of bud-scales.

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 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 on a specimen from the Lower Rhaetic of Scania, at first regarded as a megastrobilus and on further examination 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.

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, 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, 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 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 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: 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 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 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 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 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 been called to some wholly misleading and incorrect statements made by Schuster which vitiate the value of his descriptions.

Saporta 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.