Fossil plants, Vol. 3

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.

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.

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.

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).

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.

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.

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[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, 58–65µ 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.

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.

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].

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.