The fronds from the Jurassic rocks of Graham Land, described by Halle as Zamites antarcticus[1478], are very similar to some forms of P. pecten and to P. boreale and other Greenland forms; the linear subacute pinnae are attached to the upper face of the rachis at a wide angle and the base of the lamina is truncate and may be very slightly constricted. The veins are dense, as many as 5 in 1 mm., and they are occasionally forked near the base (fig. 598, A).
This Graham Land species (fig. 598, B), referred by Halle to Zamites[1479], is of the same general type as P. pecten, but is characterised by a coarser venation and by the wider angle of attachment of the pinnae.
Goeppert[1480] proposed the name Pterophyllum Dunkerianum for some specimens from the Wealden of North Germany which were afterwards figured by Dunker[1481]. Miquel[1482] included the species in his genus Dioonites and this name has been adopted by other authors. Attention has been drawn to the inconsistent use of the title Dioonites[1483], and I have previously employed the name in a sense similar to that in which it has been adopted by Nathorst, that is for fronds with long and narrow pinnae without any basal constriction and not auriculate, attached more or less at right-angles to the upper face of the rachis; but so defined Dioonites differs in no essential particular from forms of Ptilophyllum or from fronds referred by authors to Schimper’s genus Ctenophyllum. The name Ctenophyllum[1484] was instituted for certain fronds differing in some points from Otozamites and Dioonites. One such type is Ctenophyllum (Ptilophyllum) pecten (Lind. and Hutt.): this is quoted in Zittel’s Handbuch as a typical representative of the genus. Schimper followed Feistmantel in his definition of Ptilophyllum, a definition which is not in accordance with the characters of the fronds on which it was founded by Morris. Fontaine, on the other hand, has applied Ctenophyllum to fronds of a different type which are now included in the genus Pseudoctenis. There would seem to be no adequate ground for the retention of Ctenophyllum as a generic designation.
The Wealden species P. Dunkerianum is characterised by the following features: rachis fairly stout, pinnae approximate, linear 2–3 mm. broad and reaching a length of 11 cm. or more, gradually narrowed towards the apex, attached in two almost contiguous rows to the upper face of the frond-axis: the lower margin of the lamina may be slightly decurrent, e.g. in the apical part of the frond or very slightly broadened and bluntly rounded. The pinnae are attached at right-angles or, near the apex, obliquely; veins 5–6, parallel. The epidermal cells as figured by Schenk[1485] have very sinuous walls and are identical with those of the English and Indian forms of the group-species P. pecten; the stomata are confined to the lower surface. If Schenk’s drawings of the stomata are correct they differ from those of other species of the genus in their simpler structure; there are no subsidiary cells and the guard-cells show no cuticularised bands. In habit this species resembles Encephalartos Ghellinckii Lehm. (fig. 382). The superficial resemblance of the narrow linear pinnae to those of Cycadites led Dunker and Schenk to refer to that genus some specimens which have since been described as identical with P. Dunkerianum.
In the first instance the generic name Zamites was used in addition to Zamia for certain pinnate fronds including species[1486], such as Z. Bechei, which are now regarded as typical examples of Otozamites. Subsequently Brongniart gave up Zamia for fossil fronds and applied Zamites to fronds with entire pinnae, not truncate at the apex and not decurrent but slightly constricted at the base. Braun’s two genera Podozamites and Pterozamites were relegated to the position of subgenera. The name Podozamites has been employed by Schenk[1487] for specimens now included in Zamites, and Zamites is used by him[1488] for some fossils which are examples of Podozamites as generally understood. Goeppert’s definition[1489] of Zamites includes fronds with pinnae of the Otozamites type, and this author pertinently compares Zamites with recent Encephalartos leaves. Pomel[1490] proposed the name Crossozamia for certain fronds of the Zamites type, but this genus with several others instituted by the same author has not been adopted. Bornemann[1491] described Zamites as comprising species with a greater or less resemblance to the fronds of recent Zamias.
As defined below, Zamites fronds may be compared with those of some species of Encephalartos, Ceratozamia, and Macrozamia. There has been considerable difference of opinion with regard to the range of form in the pinnae that it is advisable to include in Zamites. The name Zamiophyllum was proposed by Nathorst[1492] for a Wealden species, described by Ettingshausen as Pterophyllum Buchianum (fig. 601, A–C), characterised by a decrease in the breadth of the linear pinnae towards the point of attachment and, according to Nathorst’s description, by the lateral attachment of the pinnae. An examination of specimens of this type from English rocks[1493] enabled me to show that the pinnae are attached to the upper face of the rachis. Zeiller[1494] has also included Zamiophyllum in Zamites, but Halle’s recent definition[1495] of the latter genus excludes fronds of the Zamiophyllum type. Schimper instituted the name Glossozamites[1496] for fronds bearing pinnae with rounded and slightly contracted bases and borne on grooves on the upper surface of the rachis (fig. 601, F). In venation the pinnae agree with those of Otozamites but the base is not auriculate. Kurr’s Liassic species Pterophyllum oblongifolium[1497] included by Schimper in Glossozamites is probably an Otozamites. Another species referred to this genus is Schenk’s Podozamites Zitteli[1498] from the Urgonian of Austria (fig. 601, F): in this species the slightly falcate pinnae with obtuse apices have rounded and not auriculate bases and there is some evidence of a basal callosity. This species agrees so closely with such a typical Zamites as Z. gigas that it is difficult to see on what grounds the retention of Glossozamites is desirable. A Portuguese specimen referred by Saporta[1499] to Glossozamites, G. brevis, is founded on a single specimen very like a leaflet of Otozamites Klipsteinii (Dunk.); and G. parvifolia Yok.[1500] from China has no claim to be included among Cycadean fronds. Feistmantel’s Glossozamites Stoliczkanus[1501] is almost certainly a leaf of Cordaites. For certain fronds originally described as Zamites Zeiller[1502] has instituted the genus Plagiozamites. An important question as to the type of frond which may conveniently be included in the genus Zamites was raised by the application of this name by Heer to some Lower Cretaceous fronds from Greenland, Z. borealis (= Ptilophyllum boreale, fig. 597), and others which differ in the form of the pinnae from species usually regarded as typical of the genus. Halle[1503] accepts the Greenland species as examples of Zamites though he distinguishes them by a sectional name Sub-Zamites; he defines Zamites as including fronds with pinnae attached to the upper face of the rachis with a contracted and always symmetrical base though in some cases the basal contraction is exceedingly small; there is a more or less distinct basal callosity. He recognises two types, (i) Eu-Zamites, e.g. Zamites gigas (fig. 599), in which the pinnae are strongly contracted basally and have a callosity, and (ii) Sub-Zamites, e.g. Z. borealis[1504], etc., in which the pinnae are not so broadly rounded at the base and retain the same breadth to the point of insertion where they are ‘very rapidly and very little contracted,’ with or without a basal callosity. The basal callosity in these forms is not shown in many of the pinnae and is at most but a slight rounding of the angles of the truncate base. The specimens referred by Halle to Sub-Zamites do not appear to differ in any feature worthy of generic rank from Ptilophyllum.
In the following definition Zamites is employed in a sense more or less in accordance with Brongniart’s usage but with the inclusion of such forms as Z. Buchianus, the type of Nathorst’s Zamiophyllum, and the exclusion of Heer’s Arctic and Halle’s Antarctic fronds referred by them to Zamites.
Fronds broadly lanceolate reaching a length of over 60 cm.; pinnae more or less oblique or at right-angles to the rachis (fig. 599), attached to the upper surface but not completely covering it, linear or linear-lanceolate, acuminate or obtuse, usually abruptly contracted at the rounded base and more rarely (e.g. Z. Buchianus, fig. 601) gradually tapering to the proximal end, with or without a callosity at the symmetrical base; veins divergent at the base, simple or dichotomously branched, for the most part parallel to the edges of the lamina and slightly divergent in the apical region. The presence of a basal callosity, such as is best seen in the pinnae of recent species of Macrozamia, is not a feature of great importance and cannot be easily recognised in many impressions. In the process of fossilisation the pinnae are often flattened against the surface of the rachis and this may produce transverse wrinklings of the lamina suggestive of a basal thickening. In some cases stems of the Bucklandia type occur in connexion with Zamites fronds (fig. 541). An account of these stems, and of inflorescences of Williamsonia which were borne by some at least of the plants with Zamites leaves is given in Chapter xxviii. In such examples of Zamites as have been examined the epidermal cells have sinuous walls and the stomata[1505], confined to the lower face of the lamina, occur in rows with their long axis at right-angles to that of the pinnae.
Zamites ranges from Rhaetic to Lower Cretaceous strata.
A Rhaetic species from Tonkin[1506] characterised by oval linear pinnae given off at a wide angle, alternate and not contiguous; apex obtusely truncate, gradually narrowed to a cuneate base which is rounded or elliptical and has a more or less definite callosity. The pinnae vary from 3 to 5 cm. in length and from 5 to 13 mm. in breadth.
The specific name gigas is retained in preference to that of Mantelli employed by Brongniart[1507] on the ground that he afterwards discarded it in favour of the designation proposed by Lindley and Hutton[1508], and because their name has been generally adopted.
Fronds large, exceeding 60 cm.; broadly linear lanceolate; the comparatively slender rachis bears alternate linear lanceolate pinnae with a rounded and usually slightly swollen base and an acuminate apex. At the apex of the frond the pinnae are narrow and linear (fig. 599) and almost parallel to the rachis; in the lower part they are shorter and relatively broader and attached approximately at right-angles. The numerous veins diverge from the centre of the base but for the most part are parallel to the edge of the lamina. The form of the epidermal cells and the structure of the stomata have recently been described by Mr Thomas. The external features of the stem (fig. 541) are described under the genus Williamsonia. In the case of fronds of this type from English Jurassic rocks it would be legitimate to speak of them as Williamsonia gigas, but in view of the fact that such fronds usually occur as detached specimens and without any associated flowers it is advisable, as Nathorst maintains, to retain the non-committal genus Zamites.
This type of frond is widely distributed in Jurassic strata. The occurrence of many forms agreeing generally with the type-specimen but differing from it in features that are not constant or of real morphological importance renders accurate specific delimitation very difficult. Species that appear to be indistinguishable from Zamites gigas by any well-marked characters are, Zamites Feneonis[1509] Brongn., Z. Moreaui[1510] Brongn., Z. Renevieri[1511] Heer, and Z. claravallensis[1512] Sap.; similarly Z. Schmiedelii And.[1513] is probably identical with Z. gigas. The Lower Cretaceous species Zamites bohemicus[1514] Vel. and Z. iburgensis[1515] Hos. and von d. Marck represent very similar forms.
This species was originally described by Tate[1516] as Palaeozamia (Otozamites) recta from Wealden strata in South Africa and subsequently transferred to Zamites[1517]; it bears a very close resemblance to Z. gigas. The fronds bear alternate linear pinnae attached to the upper face of the rachis by a slightly contracted and swollen base. The lamina has an acuminate asymmetrical apex and the upper edge is slightly falcate; the larger pinnae are over 6 cm. long and nearly 1 cm. broad; the veins are frequently forked as they converge towards the base of the lamina. No clear evidence of association of these fronds in the Uitenhage series of South Africa with Williamsonia flowers has been discovered, but a specimen[1518] in the Tate collection in the British Museum may be a badly preserved cluster of bracts belonging to a Williamsonia. The rachis of this species shows some peculiar features in the form of two rows of alternate cushions in some partially decayed specimens. One of these is shown in fig. 600; the cushions are raised oval projections with a flat top, and pieces of the rachis without pinnae might easily be mistaken for a Coniferous stem.
A species founded on specimens from the Wealden of Sussex[1519] and recorded from Kimmeridge beds in Scotland[1520], characterised by linear or linear-elliptical pinnae attached obliquely to the outer part of the upper surface of the rachis, somewhat abruptly narrowed at the proximal end but slightly broadened at the actual base (fig. 601, D, E). The pinnae appear to have been caducous and, as in fig. 601, D, the position of an absciss-layer is occasionally visible. In habit the fronds bear a close resemblance to those of Encephalartos longifolius Lehm. The veins diverge from the base and are for the most part parallel, though divergent at the bluntly rounded apex. If, as may be the case, a specimen figured by Hugh Miller[1521] from Scotland as Zamites and subsequently named by Richards[1522] Podozamites Milleri is identical with Z. Carruthersi, the specific name Milleri has priority.
A Wealden and Lower Cretaceous species[1523] (figs. 601, A–C; 602) represented in several European localities, also in North America and Japan, reaching a length of over 70 cm.; in habit very similar to Ceratozamia mexicana, Macrozamia Macleayi and some other recent Cycads. The rachis has a fairly broad median groove on the upper surface; pinnae alternate, opposite or sub-opposite, from 3 to 20 cm. long and from 1·5 to 2 cm. broad, linear, generally narrowed towards the base, but in the more slender segments the reduction in breadth is less obvious; attached obliquely to the rachis, slightly thickened and broadened at the base (fig. 601, C), separated from the rachis by a distinct absciss-layer and leaving an elliptical scar; usually inclined at about 45° but the angle varies considerably in different parts of a frond (fig. 602); apices generally tapering to a point, or more or less obtusely rounded; veins numerous, parallel, and not as a rule prominent. It is by no means unlikely that specimens figured by Goeppert[1524] and some other authors as Pterophyllum saxonicum or Dioonites saxonicus are examples of this species. Fontaine[1525] speaks of Dioonites Buchianus as one of the most widely distributed and characteristic members of the Potomac flora and it is described from Japan by Yokoyama[1526] and Nathorst[1527]. This type appears to be especially characteristic of Wealden strata.
Braun[1528] proposed the name Otozamites for certain Mesozoic fronds formerly included in Zamites, one of his types being Otozamites obtusus (Lind. and Hutt.) (fig. 603, B) originally regarded by Brongniart as a Fern and named Filicites Bucklandi[1529]. The auriculate form of the base of the pinnae and the spreading veins were emphasised in the definition of the genus. As in the case of many other Cycadean fronds the limits of the genus are not always easy to define, but as described below the genus is on the whole fairly distinctive. It is a very widely spread Jurassic type and extends from Triassic to Lower Cretaceous rocks. The supposed Cretaceous species from Greenland, O. groenlandica Heer[1530], is probably not a plant-impression but a polished groove in the rock.
Fronds pinnate, reaching a length of 50 cm. or more in some species; pinnae alternate, separate or contiguous and imbricate, attached by a portion of the base to the upper surface of the rachis, long and narrow (fig. 603, A), broadly oval or almost orbicular, apex acute or obtuse, base auriculate and asymmetrical[1531], the anterior lobe being more prominent than the posterior edge of the lamina which is usually rounded. The veins radiate from the base and pass obliquely with occasional branching to the edge of the pinna; in the more linear pinnae the veins may be parallel or nearly so. Zigno[1532] figured a piece of an Otozamites frond from Jurassic Italian strata in connexion with a Williamsonia and the actual specimen in the Padua Museum amply justifies the impression produced by the published drawing. Wieland’s investigations[1533] in Mexico have brought to light many cases of association of Otozamites fronds and Williamsonia flowers.
The structure of the epidermis is partially described by Schenk[1534] and more fully by Thomas[1535]: the epidermal cells have sinuous walls and the stomata, apparently confined to the lower surface, have guard-cells with hemispherical or spindle-shaped thickened patches like those of some Zamites fronds. In one species, O. Feistmanteli Zig., Thomas found about 100 stomata in 1 sq. mm. of lamina forming almost contiguous lines between the veins. In the account of the genus Ptilophyllum reference is made to the occurrence of pinnae with asymmetrical and auriculate bases, and it is only by the comparison of a large number of specimens that a distinction can be drawn between fronds that should be assigned to Otozamites and forms of Ptilophyllum which exhibit a well-marked tendency towards the Otozamites type of pinna (cf. figs. 592, 593). The variation in the form of the apices of pinnae and the relative position of the pinnae in different parts of the same frond are features worthy of notice in the determination of species[1536]. The different appearance presented by an Otozamites frond as viewed from the upper and lower face is illustrated in fig. 604. There are no recent Cycads in which the segments have auriculate bases, but in this feature as in the sinuous epidermal walls Otozamites agrees with some species of the Fern Aneimia, e.g. A. rotundifolia Schrad. (fig. 223, Vol. ii. p. 288).
There is considerable confusion in the nomenclature of this species described by Brongniart[1537] from Jurassic strata as Filicites Bechei: in it Brongniart included a specimen from the Lias of Axminster (Dorsetshire) previously figured by De la Beche as a fossil Fern. It was on the Axminster specimen that Lindley and Hutton founded the species Otopteris obtusa[1538], and as there is no doubt as to the specific identity of their type-specimen (fig. 603, B) and De la Beche’s fossil, Brongniart’s designation has prior claim[1539]. Otozamites Bechei is, perhaps, best regarded as a comprehensive type or a group-species in which numerous Otozamites fronds described by authors, on inadequate grounds, as distinct species may well be included. Fronds agreeing generally with O. Bechei were very widely spread in Rhaetic and Jurassic floras.
Specimens from the Middle Jurassic rocks of Yorkshire have been described as Otozamites obtusus var. ooliticus[1540] to denote a slight difference in the form of the pinnae from the Liassic fronds from Dorsetshire; but the distinctive features of the variety ooliticus are unimportant and hardly worthy of consideration in a general account of the species interpreted in a wide sense.
Fronds pinnate; pinnae usually more or less falcate, occasionally straight and with parallel sides, attached obliquely to the upper side of the rachis; imbricate or separate, the upper edge of the base of the lamina strongly auriculate, the lower edge rounded; apex obtuse; veins strongly divergent especially in the lobed base and extending obliquely to the upper and lower edge of the lamina.
The specimen, from the Lias of Lyme Regis, drawn in outline in fig. 605, is an almost perfect frond: the pinnae are obtusely pointed, slightly falcate, and there is a prominent lobe on the upper edge of the base of the laminae.
The Jurassic species Otozamites graphicus[1541] (Leck. ex Bean MS.), O. vicetinus Zig.[1542], O. Hennocquei[1543] (Pom.), O. recurrens Sap., O. Terquemi[1544] Sap., O. linearis[1545] Halle, are some of many examples of fronds agreeing closely with O. Bechei, or in the case of O. Terquemi with O. graphicus. The fronds described by Halle from Graham Land as O. linearis afford a good illustration of the range of variation in the pinnae: a characteristic feature is the considerable length, exceeding 20 cm., of the narrow linear fronds. The impressions from the Kome (Cretaceous) beds of Greenland described by Heer as Glossozamites Schenkii[1546] are probably closely allied to O. Bechei. The Rhaetic species O. Bucklandi Schenk[1547], O. indosinensis Zeill.[1548], and O. Polakii Krass[1549], illustrate older examples of closely allied types. Zeiller records Otozamites pinnae similar to those of O. indosinensis from Rhaetic beds in Persia[1550].
Founded on a specimen in the Scarborough Museum from the Middle Jurassic of Yorkshire[1551] which is indistinguishable from Leckenby’s type-specimen of Otopteris mediana[1552] in the Sedgwick Museum, Cambridge. Long and narrow fronds exceeding 20 cm. in length, characterised by the broadly oval, deltoid or sub-orbicular pinnae, separate or partially imbricate and attached by a broad auriculate base; apex bluntly rounded; veins numerous and spreading from the base of the lamina. The pinnae, which may be 3·5 cm. long and nearly 2 cm. broad, are narrower and longer in the distal part of the frond (fig. 606).
The Italian Jurassic species Otozamites molianus Zig.[1553], recorded also from Bornholm, is a very similar type. The generic name Cyclozamia suggested by Pomel for this form of frond has not been adopted though it is applied by Schimper to O. Bunburyanus Zig.
A Jurassic species[1554] similar in the long and narrow form of the frond to O. Beani but distinguished by the much smaller segments and by their more orbicular lamina (fig. 606, B). In habit the fronds agree closely with the Fern Nephrolepis Duffi. Leckenby’s species, Otopteris tenuata[1555], is probably the same as Zigno’s O. Bunburyanus, the type-specimen of which in the Padua Museum consists of a long and narrow frond with leaflets not exceeding 8 cm. in length; the rachis is hidden by the imbricate auriculate bases of the leaflets. Feistmantel[1556] refers to this species some pieces of very narrow fronds with overlapping pinnae from Upper Gondwana beds in India. A still smaller form is described by Möller[1557] from Bornholm as O. tenuissimus, and O. Bunburyanus is recorded from the same flora. O. Feistmanteli Zig.[1558] agrees in the form of the frond and in its short and broad pinnae with O. Bunburyanus.
This Indian species from the Rajmahal Hills[1559] and specimens of the same type from the Cutch flora described as O. contiguus Feist. afford another illustration of long and narrow fronds with short and relatively broad pinnae. The drawings published by Oldham and Morris accurately represent the specimens: the longest frond is 21 cm. long and neither end is complete (fig. 607); it is 9 mm. broad at the narrower end and 1·5 cm. at the broader end. The rachis is represented by a deep and broad groove; the actual bases of the leaflets are not preserved, but their position shows that they were attached to the upper face: this is clearly seen in the specimen described by Feistmantel as O. contiguus which shows also that the lamina is auriculate at the upper edge of the base. The pinnae vary in shape; the smaller ones are characterised by a strongly curved lower margin and the upper edge is slightly curved or straight, while the larger leaflets have more parallel edges and blunter rounded apices: the latter form is well shown in the specimens unnecessarily distinguished by Oldham and Morris as var. obtusa.
This Wealden species, first described by Dunker as Cyclopteris Klipsteinii[1560], is remarkable for the large pinnae. The rachis is fairly stout; the broadly oval or oblong pinnae vary considerably in size and in the relation of breadth to length, in rare cases reaching a length of over 8 cm. and a breadth of 2·4 cm.; apex obtuse, base slightly auriculate and asymmetrical; veins numerous, radiating from the point of attachment to the margin of the lamina. The occurrence of finer lines between the more prominent veins may indicate the presence of hypodermal stereome strands. Fig. 608 illustrates the striking variation in the size of the pinnae on a single frond and their attachment to the upper face of the rachis. In the breadth of the segments O. Klipsteinii resembles O. Beani (Lind. and Hutt.), O. decorus Sap.[1561], O. lagotis Brongn.[1562] and two species from South Russia described by Thomas[1563] as O. Izuimensis and O. giganteus. The pinnae of O. giganteus exceed 10 cm. in length and 3 cm. in breadth, thus surpassing the largest segments of O. Klipsteinii. Some pinnae from the Jurassic flora of Oregon made by Fontaine the type of a new species, O. oregonensis[1564], may be fragments of O. Klipsteinii. Nathorst[1565] records the occurrence in Lower Cretaceous or Wealden beds in Spitzbergen of Cycadean leaflets very like those of O. Klipsteinii.
This Wealden species, named by Dunker[1566] Pterophyllum Goeppertianum, agrees in habit with some of those to which reference is made under O. Bechei, e.g. O. linearis Halle, and represents a type of the genus with unusually narrow pinnae (fig. 603, A). The auriculate form of the lamina is feebly developed; the linear-lanceolate pinnae are occasionally falcate and have acute apices; as in many other species they were apparently deciduous. It is by no means easy to distinguish some of these fronds from specimens included in Ptilophyllum pecten.