Fossil plants, Vol. 2

In the specimen of Glossopteris Browniana shown in fig. 339 several leaves are attached to an axis which shows none of the surface-features of Vertebraria. I am indebted to the kindness of Dr Mohlengraaff of Delft for the loan of this specimen which was obtained from Permo-Carboniferous rocks in the Transvaal. An axis figured by Etheridge[1324] from an Australian locality bears a tuft of Glossopteris leaves, possibly G. Browniana; in place of the rectangular areas characteristic of Vertebraria it shows transversely elongated leaf-scars or, on the internal cast, imbricate rod-like projections which Etheridge suggests represent vascular bundles.

Glossopteris indica, Schimper. Figs. 340, A, 341.

It is a question of secondary importance whether or not the fronds which Brongniart spoke of as a variety of Glossopteris Browniana should be recognised as specifically distinct. The careful examination by Zeiller of the venation characters has, however, afforded justification for separating G. Browniana and G. indica. We must admit that the slight and not very constant differences in the size and form of the meshes produced by the anastomosing of the lateral veins are characters which cannot be recognised as having more than a secondary value, though, as a matter of convenience, we employ them as aids to determination. The arbitrary separation of sterile leaves, which differ by small degrees from one another in form and in the details of venation, by the application of specific names is a thankless task necessitated by custom and convenience; it is, however, idle to ignore the artificial basis of such separation. Mr Arber has recently published, in his valuable Glossopteris Flora, an analytical key which serves to facilitate the description and determination of different types of frond[1325].

The large leaves of Glossopteris indica, reaching a length in extreme cases of 40 cm. and a breadth of 10 cm., are characterised by a rather greater regularity in the arrangement of the meshes and by the greater parallelism of the upper and lower sides of each mesh (fig. 341) and by less difference in size between the venation meshes than in G. Browniana, the leaves of which are usually smaller. The relatively thick epidermis consists of rectangular cells with stomata in depressions[1326]. The scale-leaves[1327], rather larger than those of G. Browniana, are more or less rhomboidal with rounded angles and reach a length of 1·5–6 cm. and a breadth of 1·5–2·5 cm. The rhizome is practically identical with that of G. Browniana[1328].

This species occurs in great abundance in the Permo-Carboniferous rocks of India, Australia, and in various parts of South Africa, and elsewhere. It has been recognised also by Amalitzky[1329] in Upper Permian beds in Russia and by Zeiller in the Rhaetic series of Tonkin[1330].

Glossopteris angustifolia, Brongniart. Figs. 340, B; 342.

It is convenient to retain this designation for linear fronds with an acute or obtuse apex and a venation-reticulum composed of long and narrow meshes (fig. 340, B). It is by no means unlikely, as Arber suggests, that the same plant may have produced leaves of the G. indica type and narrower fronds which conform to G. angustifolia. In his description of some Indian specimens of G. indica, Zeiller draws attention to the variation exhibited in regard to the extent of anastomosing between the secondary veins: some examples with very few cross-connexions agree more closely with Taeniopteris than with Glossopteris as usually defined[1331]. The venation shown in fig. 342 illustrates an extreme case of what is almost certainly a Glossopteris leaf of the G. angustifolia type. This specimen, which was discovered by Mr Leslie in the Permo-Carboniferous sandstone of Vereeniging (Transvaal), has been referred to a variety of Brongniart’s species as G. angustifolia var. taeniopteroides[1332] on account of the almost complete absence of any cross-connexions. The reference to Glossopteris, which my friend Dr Zeiller suggested, is amply justified by the form of the leaf as a whole, by the angle at which the lateral veins leave the midrib, a feature in contrast to the wider angle at which the lateral veins are usually given off in Taeniopteris (figs. 329, 332), and by the similarity to the Indian specimens already mentioned. Several authors have described leaves or leaflets under the generic name Megalopteris[1333] from Carboniferous and Permian rocks which bear a close resemblance to the South African variety, but in some cases at least Megalopteris is known to be a pinnate and not a simple leaf. The leaf figured by Jack and Etheridge as Taeniopteris sp.[1334] from Queensland may also be an example of Glossopteris. Comparison may be made also with the Palaeozoic leaves described in the first instance by Lesquereux and more recently by Renault and Zeiller as species of Lesleya[1335] (fig. 347).

Blechnoxylon talbragarense, Etheridge. Fig. 343.

Under this name Etheridge[1336] described some specimens from the Permo-Carboniferous Coal-Measures of New South Wales, which he regards as a fern, comparable, in the possession of a cylinder of secondary xylem, with the recent genus Botrychium and with Lyginodendron and other members of the Cycadofilices. The slender axis (1–3 mm. in diameter) appears to consist of a zone of radially disposed tissue (fig. 343, C, x), which is probably of the nature of secondary xylem, enclosing a pith and surrounded externally by imperfectly preserved remnants of cortex. Unfortunately no anatomical details could be made out, but the general appearance, if not due to inorganic structure, certainly supports Etheridge’s determination. The stem bore at intervals clusters of linear-lanceolate leaves (reaching 12 mm. in length) in close spirals (fig. 343, A and B); the leaves are characterised by a strong midrib and forked secondary veins. Small “pyriform” bodies of the nature of scale-leaves occur in association with the fronds (fig. 343, B, s).

In his description of this interesting plant, Etheridge quotes an opinion which I expressed in regard to the comparison of the stem with those of Botrychium, Lyginodendron, and other genera. No satisfactory evidence has been found as to the nature of the fructification. Although the leaves of Blechnoxylon are much smaller than those of Glossopteris, I am now disposed to regard the genus as closely allied or even generically referable to Glossopteris. The crowded disposition of the leaves is like that in Glossopteris, shown in fig. 339 and in the figures published by Etheridge and by Oldham; the association of scale-leaves and foliage-leaves is another feature in common. The absence of a reticulum of anastomosing veins can no longer be considered a fatal objection to the suggestion that the Australian type may be a species of Glossopteris. If the view that Blechnoxylon is not a distinct genus is correct, the occurrence of secondary xylem is favourable to the opinion already expressed that Glossopteris is more likely to be a Pteridosperm than a true fern. The data at present available render it advisable to retain Mr Etheridge’s name: the comparison with Glossopteris lacks confirmation.

Glossopteris retifera, Feist. Fig. 344.

In some Glossopteris leaves the anastomosing secondary veins form a coarser reticulum, as in the example represented in fig. 344. The name G. retifera was given by Feistmantel[1337] to Indian fronds of this type; similar forms have been described as G. conspicua and G. Tatei. The type illustrated by G. retifera is recorded also from Permo-Carboniferous rocks in Zululand[1338], Natal, the Transvaal, Cape Colony, and the Argentine.

Gangamopteris.

In 1847 McCoy[1339] described a leaf-fragment from Permo-Carboniferous rocks in New South Wales as Cyclopteris angustifolia. The type-specimen of this species, which is now in the Sedgwick Museum, Cambridge, has been re-described by Mr Arber[1340]. Subsequently[1341] McCoy instituted the generic name Gangamopteris for leaves, like that previously referred by him to Cyclopteris, from the Bacchus Marsh Sandstone, of New South Wales, but he did not publish a diagnosis of the genus until several years later[1342]. Feistmantel[1343], who has described many species of Gangamopteris from the Lower Gondwana strata of India, slightly modified the original diagnosis. The genus is represented by sterile fronds only. We know nothing of the stem, and such evidence as is available in regard to the form of the fertile leaves is of a circumstantial kind. It is, however, highly probable that Gangamopteris is not a true fern but a Pteridosperm.

Leaves simple, sessile, varying in shape; obovate or spathulate, broadly lanceolate or rarely linear; the apex is usually blunt (fig. 345) but occasionally gradually tapered. In general appearance a Gangamopteris leaf is similar to that of Glossopteris indica, the chief distinction being the absence of a midrib. Gangamopteris leaves are on the whole larger than those of Glossopteris; many of them reach a length of 20 cm. and some of the large Indian fronds are nearly 40 cm. long. The venation of Gangamopteris shows a greater uniformity in the size and shape of the meshes than that of Glossopteris. The middle of the lamina, especially in the lower part, is occupied by a few vertical veins from which branches curve upwards and outwards towards the edge of the lamina. The secondary veins are connected by frequent anastomoses and agree very closely with those of Glossopteris. The lamina becomes narrower towards the base, which is either cuneate or in some cases slightly auriculate (fig. 345).

As I have elsewhere pointed out[1344], the presence or absence of a midrib is not in itself a character of real taxonomic importance. In the recent fern Scolopendrium vulgare the frond has a prominent midrib, while in S. nigripes there is no median rib. Mr Arber has expressed the opinion that “it is extremely doubtful whether the genus Gangamopteris should not be merged in Glossopteris[1345].” The retention of the two names is, however, convenient, and it would tend to confusion were we to carry to its logical conclusion the view that the recognised distinction between the two genera may not be a mark of generic difference.

Gangamopteris is confined to Palaeozoic strata, a fact which leads White[1346] to speak of the Gangamopteris rather than of the Glossopteris Flora. It occurs in South America, South Africa, Australia, and India, extending as far north as Kashmir; it has been discovered by Amalitzky in Permian rocks of Russia[1347]. The Russian rocks in which Glossopteris and Gangamopteris were found are no doubt of Permian age. In Australia, South Africa, Brazil and Argentina, and in the Indian Coal-fields, Gangamopteris is a characteristic genus of Lower Gondwana rocks. These strata are usually spoken of as Permo-Carboniferous in order to avoid the danger of attempting on insufficient data a precise correlation with European formations.

Feistmantel speaks of Gangamopteris as most abundant in the Talchir-Karharbári beds, though it is represented also in the overlying Damuda series. In Australia the genus occurs in rocks which correspond in position and in their plant fossils with the Talchir-Karharbári beds of India; similarly, in South Africa and South America the Gangamopteris beds are homotaxial with those of India and Australia. The leaf described by Carruthers[1348] from Brazil as Noeggerathia obovata (the type-specimen is in the British Museum) is no doubt specifically identical with Gangamopteris cyclopteroides Feist.[1349] In a paper by Mr Hayden on Gangamopteris beds in the Vihi Valley, Kashmir, evidence is adduced in support of the conclusion that the rocks are “not younger than Upper Carboniferous and may belong to the base of that subdivision or even to the Middle Carboniferous[1350].” It would seem that Gangamopteris was a very widely spread genus during the latter part of the Carboniferous period in the vast Southern Continent to which the name Gondwana Land is often applied, and that it flourished in the Southern Flora during at least part of the Permian period: with other members of the Glossopteris Flora it migrated to the North where it has been preserved in Permian rocks of Northern Russia. The Glossopteris Flora must have had its birth in the Southern hemisphere. The conclusion seems inevitable that the leaves of Glossopteris and Gangamopteris in the shales and sandstones of India, South Africa, South America, and Australia are relics of the vegetation of a continent of which these regions are the disjuncta membra. Darwin wrote to his friend Hooker in 1881, “I have sometimes speculated whether there did not exist somewhere during long ages an extremely isolated continent, perhaps near the South Pole[1351].” It is probable that Gangamopteris is one of the genera which flourished on this continent.

Gangamopteris cyclopteroides, Feistmantel[1352]. Fig. 345.

The specimen represented in fig. 345 illustrates the characters of this commonest representative of the genus.

Gangamopteris kashmirensis, Seward.

This type agrees closely with G. cyclopteroides in size and in the form of the leaf, but it is distinguished by the flatter form of the arch formed by the lateral veins, by their greater inclination to the margin of the lamina, and by the more acutely pointed apex of the lamina. This species, though not very sharply distinguished from G. cyclopteroides, is important as coming from beds which have been assigned on other than palaeobotanical evidence to an Upper or possibly a Middle Carboniferous horizon[1353].

We have no definite information in regard to the nature of the reproductive organs of Gangamopteris, but such evidence as there is supports the view expressed by Dr White[1354] and shared by some other authors that Gangamopteris and Glossopteris should be assigned to the Pteridosperms. Despite the abundance of Gangamopteris leaves, no fertile specimen has been discovered. This negative evidence may prove to be as correct as that which led Stur[1355] to exclude Neuropteris, Alethopteris and Odontopteris from the ferns. The only evidence of a positive kind is that furnished by Dr David White in his recent Report on the Palaeozoic Flora of South Brazil. This author describes some small Aphlebia-like leaves under two new generic names Arberia[1356] and Derbyella[1357]. The differences between the two sets of specimens, so far as can be determined from the reproductions of imperfect impressions, are slight, and it is by no means clear that a distinction of generic rank exists. These scale-leaves are on the average about 2 cm. in length; the lamina is oval or rounded and has more or less prominent lobes. In Derbyella there are indications of anastomosing veins. The specimens referred to Arberia minasica are, as White points out, very similar to the fossil described by Feistmantel from Lower Gondwana rocks of India as probably a portion of an inflorescence of Noeggerathiopsis[1358]. Feistmantel’s specimen is represented in fig. 346: the curled lobes may have originally borne seeds. In the Brazilian examples the abruptly truncated lobes “bear evidence of separation from reproductive bodies.” An important point is the association of these scale-leaves with Gangamopteris fronds and with gymnospermous seeds of the Samaropsis type. On the leaves assigned to Derbyella aurita circular depressions occur at the base of the lobes which are described as probably due to sporangia.

Dr White’s discovery gives us increased confidence in expressing the view that Gangamopteris bore its reproductive organs on specialised leaves very different from the sterile fronds; it also strengthens the suspicion that the genus is a member of the class of seed-bearing fern-like plants.

Lesleya.

This generic designation was instituted by Lesquereux[1359] for simple oval-linear leaves from the Coal-Measures of Pennsylvania. The leaves so named are probably generically identical with the specimen doubtfully assigned by Brongniart[1360] to the Coal-Measures, and made by him the type of the genus Cannophyllites on the ground of a resemblance to the leaves of the recent flowering plant Canna. Fig. 347 illustrates the form of a Lesleya leaf from the Coal-basin of Gard, named by Grand’Eury L. simplicinervis[1361], a type in which the veins are frequently unbranched and not repeatedly forked as in most examples of the genus (fig. 329, C). The features of the genus are, the oval-linear or lanceolate shape of the presumably simple frond, its entire or, in one species at least (L. Delafondi, Zeill.), finely dentate margin, the stout rachis giving off at a very acute angle numerous dichotomously branched secondary veins. In L. Delafondi (fig. 329, C), described by Zeiller[1362] from the Lower Permian of Autun, the frond may reach a length of more than 20 cm. and a breadth of 8 cm. Similar species are represented by L. ensis[1363] from the coal-field of Commentry, and L. grandis[1364] from Upper Carboniferous rocks of North America. The genus is characteristic of Upper Carboniferous and Lower Permian strata: the form of the leaf and the direction of the secondary veins suggest comparison with Glossopteris, but in Lesleya there are no cross-connexions between the veins. Nothing is known as to the fructification, a fact which naturally evokes the opinion that the genus is a Pteridosperm[1365] and not a true fern. Some years before the discovery of Pteridosperms, Grand’Eury[1366] suggested that Lesleya might be a Gymnosperm; his opinion being based on the woody nature of the rachis and on the simple venation of Lesleya simplicinervis.

Neuropteridium.

In their monograph of fossil plants from the Bunter Series of the Vosges, Schimper and Mougeot[1367] described some pinnate leaves of ferns as species of the genus Neuropteris. In 1869 Schimper[1368] placed these in a new sub-genus Neuropteridium, in order to draw attention to the fact that their fronds appear to be simply pinnate and not bipinnate or tripinnate as in Neuropteris. The type-species of Neuropteridium is N. grandifolia Sch. and Moug. from the Bunter Sandstones of the Vosges. The genus includes Triassic European species and the widely distributed Permo-Carboniferous species from Brazil[1369] originally described by Carruthers as Odontopteris Plantiana. It is probable that some Carboniferous plants, particularly species from the lower members of the formation, referred to the genus Cardiopteris, are not genetically distinct from the Indian and southern hemisphere type Neuropteridium validum (= Odontopteris Plantiana).

Fronds pinnate, linear; a broad rachis bears pinnules which may be either semicircular or broadly linear with an entire or lobed margin. The longer pinnules may exceed 6 cm. in length. The pinnules agree with those of Neuropteris in being attached by the median portion of the lamina and not by the whole base, which is more or less auriculate. In some cases the repeatedly forked veins diverge from the centre of the pinnule base; in others there is a midrib which persists for a short distance only, and in some species the more persistent median vein gives the segments a closer resemblance to those of Neuropteris. Fructification unknown, with the exception of obscure indications of sporangia (?) on the fertile leaves of a Triassic species.

Neuropteridium validum. (Feistmantel[1370]). Fig. 348.

The specimen represented in fig. 348 illustrates the main features of Neuropteridium validum. This species is referred to by Dr White[1371] as N. Plantianum on the ground of priority, and with a view to perpetuate the name of the English engineer Nathaniel Plant who discovered the species in a Brazilian Coal-field in the province of Rio Grande do Sul. Feistmantel’s specific name is however retained as being much better known. An examination of Mr Plant’s specimen in the British Museum led me[1372] to speak of the Brazilian species as identical with N. validum described by Feistmantel from Lower Gondwana rocks of India. Zeiller[1373] had previously drawn attention to the resemblance between the two sets of specimens. The frond of N. validum may exceed 50 cm. in length. The lower pinnules may be entire and semicircular in form while the upper and larger segments, which may reach a length of 5 or 6 cm., are characterised by broad lobes (fig. 348).

This type is represented in the flora of the Talchir-Karharbári series (Lower Gondwana) of India[1374], in Permo-Carboniferous rocks of Brazil and Argentine[1375], and in the sandstones of Vereeniging on the borders of the Transvaal and Cape Colony. It is a characteristic member of the Glossopteris Flora and occurs in association with Glossopteris and Gangamopteris.

Neuropteridium intermedium (Schimper). Fig. 349.

This species has been figured by Schimper and Mougeot[1376] from the Bunter of the Vosges and more fully described by Blanckenhorn[1377] from the Bunter beds of Commern. The pinnate leaves reach a length of 65 cm.; the lower semicircular pinnules pass gradually into broadly linear segments characterised by an auriculate base and a Neuropteris type of venation (fig. 354, D′, E). In the example reproduced in fig. 349 from one of Blanckenhorn’s figures, the fronds are attached to a short and thick rhizome bearing roots and portions of old petioles.

An example of another Triassic species is afforded by Neuropteridium grandifolium Schimp. and Moug., which agrees very closely with N. validum in the size and shape of the pinnules. The occurrence in Lower Mesozoic European rocks of fronds hardly distinguishable from the older southern species may be regarded as favourable to the view already expressed, that some at least of the Permo-Carboniferous plants migrated north of the Equator. The resemblance between the Vosges Triassic species of Schizoneura[1378] and the examples of this genus recorded from the Lower Gondwana rocks of India affords additional evidence of a northern migration.

Our knowledge of the reproductive organs of Neuropteridium is practically nil. There is no doubt that Zeiller[1379] and Blanckenhorn[1380] are correct in regarding the Bunter fronds assigned by Schimper and Mougeot to the genus Crematopteris as the fertile leaves of Neuropteridium intermedium or some other species from the same horizon. These fronds bear crowded pinnules similar to those of Neuropteridium intermedium, N. Voltzii[1381], and other species, exhibiting on the exposed surface numerous carbonaceous spots which may be the remains of sporangia.

Cardiopteris.

Schimper[1382] applied this generic name to Lower Carboniferous fronds of a simple-pinnate habit which had previously been described as species of Cyclopteris. Cardiopteris frondosa may serve as a typical example. This species, originally described by Goeppert as Cyclopteris frondosa (fig. 350), is recorded from Lower Carboniferous rocks in the Vosges district[1383] in Silesia, Moravia[1384], and Thuringia[1385]. The pinnules, which are attached in opposite pairs to a broad rachis, vary in length from 2 to 10 cm. and have a breadth of 2 to 8 cm.; in manner of attachment and venation they agree with those of Neuropteridium validum. The venation is very clearly shown in a drawing of some large pinnules figured by Stur[1386].

The specimen of Cardiopteris frondosa, a portion of which is shown in fig. 350 on a slightly reduced scale, was originally figured by Schimper from an unusually good example in the Strassburg Museum. Schimper’s drawing hardly does justice to the original specimen.

A frond bearing rather narrower pinnules, alternately placed on the rachis, which Fritsch has described as Cardiopteris Hochstetterii var. franconica from the Culm of Thuringia, bears a close resemblance to Neuropteridium validum but differs in the entire margin of the pinnules. An Upper Carboniferous species from Russia described by Grigoriew[1387] as Neuropteris, cf. cordata var. densineura, represents another form of similar habit.

Schuster[1388] has recently proposed a new generic name Ulvopteris for a fragment of a pinna from the Coal-Measures of Dudweiler in Germany bearing large pinnules, which he compares with those of Cardiopteris and species of Rhacopteris. The specimen appears to be indistinguishable from some of those already referred to as conforming to Neuropteridium, and it is difficult to recognise any reason for the creation of a new generic name.

We cannot hope to arrive at any satisfactory decision in regard to the precise affinity between Neuropteridium validum and species referred to Cardiopteris and other genera so long as portions of sterile fronds are the only tests at our disposal. It is difficult to determine whether a specimen consisting of an axis bearing pinnules represents a large pinna of a bipinnate frond or if it is a complete pinnate leaf. There is, however, no adequate reason for supposing that the presumably pinnate fronds from the Gondwana Land rocks are generically distinct from the Lower Carboniferous European species Cardiopteris frondosa. Granting the probability that both genera are Pteridosperms and closely allied to one another, the two generic names may be retained on the ground of long usage and in default of satisfactory evidence confirmatory of generic identity. Cardiopteris would thus stand for a type of frond characteristic of the Lower Carboniferous strata of Europe, while Neuropteridium is retained for the Southern species N. validum, and for others from the Trias of the Vosges.

Aphlebia.

This name was proposed by Presl[1389] for large leaf-like impressions having a pinnate or pinnatifid form and characterised by a confused irregular type of venation, or by a fine superficial striation or wrinkling which simulates veins. Gutbier had previously described similar fossils as Fucoides, and other authors have described Aphlebiae as species of Rhacophyllum, Schizopteris, and other genera[1390]. The term Aphlebia is retained, not as denoting a distinct genus but (i) as a descriptive name for detached leafy structures similar to those figured by Presl, which are now recognised as laminar appendages of the petioles of ferns or fern-like fronds, and (ii) as an epithet for highly modified pinnules which frequently occur at the base of the primary pinnae of Pecopteroid and Sphenopteroid fronds (e.g. Dactylotheca plumosa, fig. 293)[1391].

Modified pinnules, similar in their reduced and deeply dissected lamina to those represented in fig. 293, are frequently found at the base of the primary pinnae of Palaeozoic species of Sphenopteris and other genera of Pteridosperms or ferns, including members of the Coenopterideae. Potonié[1392] gives a list of various types of Aphlebiae in his paper on these organs. A striking case has recently been described by Zeiller in a French Upper Carboniferous species, Sphenopteris Matheti[1393]. It would seem that the larger examples of Aphlebiae are more frequently associated with the compound leaves of Pteridosperms than with those of Ferns[1394].

As examples of the larger types of Aphlebiae reference may be made to Aphlebia crispa (Gutb.)[1395], which reaches a length of nearly 60 cm. and has the form of a more or less triangular pinnate leaf divided into decurrent deeply lobed segments, to a similar species represented by A. Germari (= Schizopteris lactuca Germ.)[1396] which simulates the leaves of endive (Cichorium endivia L.), and to some large forms figured by Grand’Eury[1397] as species of Schizopteris.

Aphlebiae such as that figured by Kidston[1398] as Rhacophyllum crispum, with narrow ultimate segments, might easily be mistaken for the impressions of an alga.

The term Aphlebia may be applied also to the Cyclopteroid pinnules on the petioles of some species of Neuropteris, Odontopteris and Archaeopteris. Goebel[1399] has referred to the application by Potonié and other authors of the term Aphlebioid to the pinnules which serve as bud-protecting organs in recent fronds of Gleichenia (fig. 226, p. 290); he expresses the opinion that it is superfluous and misleading to make use of a special designation for structures which are undoubtedly modified pinnules. In the case of fossils it is, however, convenient to employ the term Aphlebia as a descriptive name for modified pinnules or stipular structures which cannot be connected with definite species of fronds. It is clear that some Aphlebiod leaflets, such as those of Dactylotheca, served as protective organs for the unexpanded pinnae[1400], and in all probability the large Aphlebiae served the same purpose as the fleshy stipules of Angiopteris and Marattia which cover the uncoiled fronds. The pinnatifid scale-leaves of considerable size (fig. 351) which occur in the leaf-axils or as ochrea-like stipules on the fronds of Gunnera (a tropical and subtropical Dicotyledonous genus) bear a very close resemblance to some Palaeozoic Aphlebiae, e.g. Aphlebia crispa (Gutb.). The recent and fossil scale-leaves may be regarded as similar in function as in form; moreover the delicate coiled fronds of Palaeozoic Pteridosperms or ferns, like those of some recent flowering plants, may have been kept moist by a secretion of mucilage. The pinnatifid stipules of Marattia fraxinea (fig. 241, B, p. 317) resemble certain fossil Aphlebiae, and the wrinkled surface of the recent stipules presents an appearance similar to that which in some fossil forms has been erroneously described as veining. It is not improbable that mantle-leaves of such recent ferns as Polypodium quercifolium (fig. 234, M, p. 303) are comparable with some fossil Aphlebiae which may have served as humus-collectors for Palaeozoic epiphytes.