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MAP A

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Originally appearing in Volume V20, Page 545 of the 1911 Encyclopedia Britannica.
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MAP A.—G,—G6, Glossopteris Flora. VI. Permian (Pechora valley). IX. Lower Jurassic, Upper Gondwana (Argentine X. Rhaetic (Persia). XI. Triassic—Cretaceous, I, II. Upper Carboniferous plants of the northern hemisphere facies, in the Zambesi district and in China. IV. Carboniferous plants (prov. Kansu). V. Glossopteris, &c., in Permian rocks in prov. Vologda. the northern and southern botanical provinces. In 1895 Professor Zeiller described several plants from the province of Rio Grande do Sul in South America (Map A, G2), including a few typical members of the Glossopteris flora associated with a European species, Lepidophloios laricinus, one of the characteristic types of the Coal period, and with certain ferns resembling some species from European Permian rocks. A similar assocjation was found also in Argentine rocks by Kurtz (Map A, GI), and from South Africa Sigillaria Brardi, Psygmophyllum, Bothrodendron and other northern types are recorded in company with Glossopteris, Glangamopteris and Naeggerathiopsis. The Coal-bearing strata which occupy a considerable area in China (Map A, II.), contain abundant samples of a vegetation which appears to have agreed in their main features with the Permo-Carboniferous floras • of the northern hemisphere. In his account of some plants from the Coal Measures of Kansu (Map A, IV.) Dr Krasser has drawn attention to the apparent identity of certain leaf-fragments with those of Naeggerathiopsis (After Feistmantel.) Hislopi, a typical member of the Glossopteris wana rocks, India. of a European genus Cordaites. A com- paratively rich fossil flora was described in 1882 from Tongking (Map A, I I I. by Professor Zeiller—and this author has recently made important additions to his original account—which demonstrates an admixture of Glossopteris types with others which were recognized as identical with plants characteristic of Rhaetic (After Feistmantel.) A. B. • rocks, India. A. nat. size. B. leaflet enlarged. Lower Gondwana strata of India (fig. 4), South America and South Africa. These two instances—the Tongking beds of Rhaetic age and the Bunter sandstones of the Vosges—afford evidence of a species which do not occur in the Glossopteris flora. Another plant found in the Vosges sandstones—Neuropteridium grandifolium-is also closely allied to species of the same " fern " recorded from the northern extension of Glossopteris types and their association with European species. In 1898 an important discovery was made by Professor Amalitzky, which carries us a step further in our search for a connexion between the northern and southern floras. Amalitzky found in beds of Upper Permian age in the province of Vologda (Russia) (Map A, V.) species of Glossopteris and Naeggerathiopsis typical members of the Glossopteris flora, associated with species of the ferns Taeniopteris, Callipteris and Sphenopteris, a striking instance of a commingling in the far north of the northern hemisphere Permian species with migrants from " Gondwana Land." This association of types clearly points to a penetration of representatives of the Glossopteris flora to the north of Europe towards the close of the Permian period. Evidence of the same northern extension is supplied by floras described by Schmalhausen from Permian rocks in the Pechora valley (Map A, VI.), the Siberian genus Rhiptozamites being very similar to, and probably generically identical with, Naeggerathiopsis of the Glossopteris flora. The Permo - Carboniferous beds of South Africa, India and Australia are succeeded by other plant-bearing strata, containing numerous species agreeing closely with members of the Rhaetic and rassic floras of the northern hemisphere. These post-Permian floras, as represented by the Upper Gondwana beds of India and corresponding strata in Australia, South Africa, and South America, differ but slightly from the northern floras, and point to a uniformity in the Rhaetic and Jurassic vegetation which is in contrast to the existence of two botanical provinces during the latter part of the Palaeozoic period. A few plants described by Potonie from German and Portuguese East Africa demonstrate the occurrence of Glossopteris and a few other genera, referred to a Permo-Triassic horizon, in a region slightly to the north of Tete in the Zambesi district (Map A, I.), where typical European plants agreeing with Upper Carboniferous types were discovered several years ago, anfl described by Zeiller in 1882 and 1901. The existence of Upper Gondwana plants, resembling Jurassic species from the Rajmahal beds of India, has been demonstrated in the Argentine by Dr Kurtz. Having seen how the Glossopteris flora of the south gradually spread to the north in the Permian period, we may now take a Meaozolc brief survey of the succession of floras in the northern M Flo. eso hemisphere, which have left traces in Mesozoic rocks of North America, Europe and Asia. Our knowledge of the Triassic vegetation is far from extensive; this is no doubt due in part to the fact that the conditions under which the Triassic rocks were deposited were not favourable to the existence of a luxuriant vegetation. Moreover, the Triassic rocks of southern Europe and other regions are typical marine sediments. The Bunter sandstones of the Vosges have afforded several species of Lower Triassic plants; these include the Equisetaceous genus Schizoneura—a member also of the Glossopteris flora—bipinnate fern fronds referred to the genus Anomopteris, another fern, described originally as Neuropteris grandifolia, which agrees very closely with a southern hemisphere type (Neuropteridium validum, fig. 4), some large Equisetaceous stems apparently identical, except in size, with modern Horse-tails. With these occur several Conifers, among others Voltzia heterophylla and some twigs referred to the genus Albertia, bearing large leaves like those of Agathis australis and some of the Araucarias, also a few representatives of the Cycadales. Among plants from Lower Triassic strata there are a few which form connecting links with the older Permo-Carboniferous flora; of these we have a species, described by Blanckenhon as Sigillaria oculina, which may be correctly referred to that genus, although an inspection of a plaster-cast of the type-specimen in the Berlin Bergakademie left some doubt as to the sufficiency of the evidence for adopting the generic name Sigillaria. Another Triassic genus, Pleuromeia, is of interest as exhibiting, on the one hand, a striking resemblance to the recent genus Isoetes, from which it differs in its much larger stem, and on the other as agreeing fairly closely with the Palaeozoic genera Lepidodendron and Sigillaria. There is, however, a marked difference, as regards the floras as a whole, between the uppermost Palaeozoic flora of the northern hemisphere and such species as have been recorded from Lower Triassic beds. There is evidence of a distinct break in the succession of the northern floras which is not apparent between the Permian and Trias floras of the south. Passing over the few known species of plants from the middle Trias (Muschelkalk) to the more abundant and more widely spread Upper Triassic species as recorded from Germany, Austria, Switzerland, North America and elsewhere, we find a vegetation characterized chiefly by an abundance of Ferns and Cycads, exhibiting the same general facies as that of the succeeding Rhaetic and Lower Jurassic floras. Among Cycads may be mentioned species of Pterophyllum (e.g. P. Jaegeri), represented by large pinnate fronds not unlike those of existing species of Zamia, some Equisetaceous plants and numerous Ferns which may be referred to such families as Gleicheniaceae, Dipteridinae and Matonineae. Representatives of the Ginkgoales constitute characteristic members of the later Triassic floras, and these, with other types, carry us on without any break in continuity to the Rhaetic floras of Scania, Germany, Asia, Chile, Tonkin and Honduras (Map A, VIII.), and to the Jurassic and Wealden floras of many regions in both the north and south hemispheres. A comparative view of the plants found in various parts of the world, in beds ranging from the Upper Trigs to the top of the Jurassic system, reveals a striking uniformity in the vegetation both in northern and southern latitudes during this long succession of ages. The Palaeozoic types are barely represented; the arborescent Vascular Cryptogams have been replaced by Cycads, Ginkgoales and Conifers as the dominant classes, while Ferns continue to hold their own. No undoubted Angiosperms have yet been found below the Cretaceous system. From the close of the Permian period, which marks the limit of the Upper Palaeozoic floras, to the period immediately preceding the apparently sudden appearance of Angiosperms, we have a succession of floras differing from one another in certain minor details, but linked together by the possession of many characters in common. It is impossible to consider in detail this long period in the history of plant-evolution, but we may briefly pass in review the most striking features of the vegetation as exhibited in the dominant types of the various classes of plants. Fragments of a Jurassic flora have recently been discovered by Dr Andersson, a member of Nordenskiold's Antarctic expedition, in Louis. Philippe Land in lat. 63° 15' S. Among other well-known Jurassic genera Nathorst has identified the following: Equisetites, Cladophlebis, Todites, Thinnfeldia, Otozamites, Williamsonia pecten, Araucarites. The discovery of this Antarctic flora is a further demonstration of the world-wide distribution of a uniform Jurassic flora. Under the head of Algae there is little of primary importance to record, but it is of interest to notice the occurrence of certain forms which throw light on the antiquity of existing families Algae. of Algae. Species referred on good evidence to the Charophyta are represented by a few casts of oogonia and stem fragments, found in Jurassic and Wealden beds, which bear a striking resemblance to existing species. There is some evidence for the occurrence of similar Chant " fruits " in middle Triassic rocks; some doubtful fossils from the much older Devonian rocks have also been quoted as possible examples of the Charophyta. The oldest known Diatoms are represented by some specimens found entangled in the spicules of a Liassic sponge, and identified by Rothpletz as species of the recent genus Pyxidicula. The calcareous Siphoneae are represented by several forms, identified as species of Diplopora, Triploporella, Neomeris and other genera, from strata ranging from the lower Trias limestones of Tirol to the Cretaceous rocks of Mexico and elsewhere. It is probable that the Jurassic Goniolina, described from French localities, and other genera which need not be mentioned, may also be reckoned among the Mesozoic Siphoneae. A genus Zonatrichites, compared with species of Cyanophyceae, has been described as a Calcareous alga from Liassic limestones of Silesia. The geological history of Mosses and Liverworts is at present very incomplete, and founded on few and generally unsatisfactory fragments. It is hardly too much to say that no Bryop6yta. absolutely trustworthy examples of Mosses have so far been found in Mesozoic strata. Of Liverworts there are a lew species, such as Palaeohepatica Rostafinskii from the Lower Jurassic (After Feistmantel.) rocks of Cracow, Marchantites erect= from the Inferior Oolite rocks of Yorkshire, and M. Zeilleri from the Wealden beds of Sussex. These fossil Hepaticae are unfortunately founded only on sterile fragments, and placed in the Liverworts on the strength of their resemblance to the thallus of Marchantia and other recent genera. The Palaeozoic Calamites were succeeded in the Triassic period by large Equisetites, differing, so far as we know, in no essential Bgalse• respect from existing Equisetums. The large stems taceae. represented by casts of Triassic age, Equisetites arenaceus and other species, probably possessed the power of secondary growth in thickness; the cones were of the modern type, and the rhizomes occasionally formed large underground tubers like those frequently met with in Equisetum arvense, E. sylvaticum and other species. Equisetites Muensteri is a characteristic and fairly widely spread Rhaetic and Liassic species, having a comparatively slender stem, with leaf-sheaths consisting of a few broad and short leaf-segments. Equisetites columnaris, a common fossil in the Jurassic plant-beds of the Yorkshire coast, represents another type with relatively stout and occasionally branched vegetative shoots, bearing leaf-sheaths very like those of Equisetum maximum and other Horsetails. In the Wealden strata more slender forms have been found—e.g. Equisetites Burchardti and E. Lyelli—in England, Germany, Portugal, Japan and elsewhere, differing still less in dimensions from modern species. Of other Equisetales there are Schizoneura and Phyllotheca; the former first appears in Lower Gondwana rocks as a member of the Glossopteris flora, migrating at a later epoch into Europe, where it is represented by a Triassic species. The latter genus ranges from Upper Carboniferous to Jurassic rocks; it occurs in India, Australia, and elsewhere in the " Gondwana Land " vegetation, as well as in Palaeozoic rocks of Asia Minor, in Permian rocks of Siberia, and in Jurassic plant-beds of Italy. This genus, like the allied Calamites, appears to have possessed cones of more than one type; but we know little of the structure of these Mesozoic Equisetaceous genera as compared with our much more complete knowledge of Calamites and Archaeocalamites. (See section I., PALAEOZOIC.) Reference has already been made to Sigillaria oculina and to the genus Pleuromeia. Palaeobotanical literature contains several Lycopo- records of species of Lycopodites and Selaginellites; dimes. nearly all of them are sterile fragments, bearing a more or less close resemblance to living Club-Mosses and Selaginellas, but lacking the more important reproductive organs. Nathorst has recently described a new type of lycopodiaceous cone, Lycostrobus Scotti, from Rhaetic rocks of Scania, from which he obtained both megaspores and microspores. An investigation by Miss Sollas of a plant long known from Rhaetic rocks in the Severn valley as Naiadita acuminate has shown that this genus is in all probability a small lycopodiaceous plant, and neither a Moss nor a Monocotyledon, as some writers have supposed. One of the best-known European species is Lycopodites falcatus, originally described by Lindley and Hutton from the Inferior Oolite of Yorkshire. Among the large number of Mesozoic Ferns there are several species founded on sterile fronds which possess but little interest Fllicales. from a botanical standpoint. Some plants, again, have been referred by certain authors to Ferns, while others have relegated them to the Cycads. As examples of these doubtful forms may be mentioned Thinnfeldia, characteristic of Rhaetic and Lower Jurassic rocks; Dichopteris, represented by some exceptionally fine Jurassic specimens, described by Zigno, from Italy; and Ctenis, a genus chiefly from Jurassic beds, founded on pinnate fronds like those of Zamia and other Cycads, with linear pinnae characterized by anastomosing veins. Plants referred to Schimper's genus Lomatopteris and to Cycadopteris of Zigno afford instances of the difficulty of distinguishing between the foliage of Ferns and Cycads. The close resemblance between specimens from Jurassic rocks placed in one or other of the genera Thinnfeldia, Dichopteris, Cycadopteris, & c., illustrates the Unsatisfactory custom of founding new names on imperfect fronds. It is of interest to note that some leaf-fragments recently found in Permian rocks of Kansas, and placed in a new get-ins Glenopteris, are hardly distinguishable from specimens of Jurassic and Rhaetic age referred to Thinnfeldia and other Mesozoic genera. The difficulty of distinguishing between Ferns and Cycads is a necessary consequence of the common origin of these two B classes; in Palaeozoic times the Cycadofilicies and Pteridospermae (see section I., PALAEOZOIC) played a prominent part, and even among recent Cycads and Ferns we still see a few indications of their close relationship. There is reason to believe that compound or generalized types—partly Ferns and partly Cycads—persisted into the Mesozoic era; but without more anatomical knowledge than we at present possess, it is impossible to do more than to point to a few indications afforded by external, and to a slight extent by internal structure, of the survival of Cycadofilicinean types. The genus Otozamites, which it is customary and probably correct to include in the Cycadales, is represented by certain species, such as Otozamites Beani (fig. 5, A), a characteristic Yorkshire fossil of Jurassic age, which in the form of the frond, bearing broad and relatively short pinnae, exhibits a striking agreement with the sterile portions of the fronds of Aneimia rotundifolia, a member of the fern family Schizaeaceae. Again, another species of the same genus, 0. Bunburyanus (fig. 5, B), suggests a comparison with fern fronds like that of the recent species Nephrolepis Duffi. The scaly ramenta which occur in abundance on the leaf-stalk bases of fossil Cycads constitute another fern-character surviving in Mesozoic Cycadales. Without a fuller knowledge of internal structure and of the reproductive organs, we are compelled to speak of some of the Mesozoic plants as possibly Ferns or possibly Cycads, and not refer-able with certainty to one or other class. It has been found useful in some cases to examine microscopically the thin film of coal that often covers the pinnae of fossil fronds, in order to determine the form of the epidermal cells which may be preserved in the carbonized cuticle; rectilinear epidermal cell-walls are usually considered characteristic of Cycads, while cells with undulating walls are more likely to belong to Ferns. This distinction does not, however, afford a safe guide; the epidermal cells of some ferns, e.g. Angiopteris, have straight walls, and occasionally the surface cells of a Cycadean leaf-segment exhibit a fern-like character. Leaving out of account the numerous sterile fronds which cannot be certainly referred to particular families of Ferns, there are several genera which bear evidence in their sori, and to some extent in the form of the leaf, of their relationship to existing types. The abundance of Palaeozoic plants with sporangia and sori of the Marattiaceous type is in striking contrast to the scarcity of Mesozoic ferns which can be reasonably included in the Marattiaceae. One of the few forms so far recorded tiaceaetMarat- . is that known as Marattia Muensteri from Rhaetic localities in Europe and Asia. Some species included in the genus Danaeites or Danaeopsis from Jurassic rocks of Poland, Austria and Switzerland may possibly be closely allied to the recent tropical genus Danaea. Of the Ophioglossaceae there are no satisfactory examples; one of the few fossils compared with a recent species, Ophioglossum palmatum, was described several years ago from Triassic rocks under the name Cheiropteris, but the resemblance is one of external form only, and practically valueless as a taxonomic criterion. It would appear that the eusporangiate Ferns suddenly sank to very subordinate position after the Palaeozoic era. The Osmundaceae, represented by a few forms of Palaeozoic age, played a more prominent part in the Mesozoic floras. A species described by Schenk from Rhaetic rocks of Franconia as Osmun-Acrostichites princes is hardly distinguishable from daceae. Todites Williamson, a widely distributed species in Inferior Oolite strata. This Jurassic species bore bipinnate fronds not unlike those of the South African, Australian, and New Zealand Fern Todea barbara, which were characterized by a stout rachis and short broad pinnules bearing numerous large sporangia covering the under surface of the lamina. Specimens of Todites have been obtained from England, Poland, and elsewhere, sufficiently well preserved to afford good evidence of a correspondence in the structure of their sporangia with those of recent Osmundaceae. This Jurassic and Rhaetic type occurs in England, (Germany, Poland, Italy, East Greenland, North America, Japan, China and Persia (Map A, X.). Bipinnate sterile fronds of Todites have in some instances been described tinder the designation Pecopteris whitbiensts. This and other names, such as Asplenium whitbiense, A. nebbense, Asplenites Roesserti,&c.,have been given to bipinnate fronds of a type frequently met with in different genera and families of recent Ferns, e.g. Onoclea Struthiopteris, species of Cyathea, Asplenium, Gymnogramme, &c. In most cases the Rhaetic, Jurassic andWealden Ferns included FIG. 6.—Cladopphlebis denticulata. under one or other of these Inferior Oolite, England. names are sterile, and can- not be assigned to a particular family, but some are undoubtedly A, Otozamites Beani. B, 0. Bunburyanus. Inferior Oolite, England. the leaves of Todites, a genus which may often be recognized by the broad and relatively short bluntly-terminated pinnules. The Jurassic species Cladophlebis denticulata (fig. 6), recorded from several European localities, as well as from North America, Japan, China, Australia, India and Persia, affords an instance of a common type of bipinnate frond similar to Todites Williamsoni, which has been included in the Polypodiaceae; but such meagre evidence of the soral characters as we possess also points to a comparison with the recent fern Todea barbara. Our knowledge of the anatomy of fossil Osmundaceae has recently been considerably extended by Kidston and Gwynne-Vaughan. (For references, see Seward, Fossil Plants, vol. ii., 1910.) The Schizaeaceae include a widely spread species, originally named Pecopteris exilis, and subsequently placed in a new genus, Klukia Schizae- (fig. 7), which is characterized by tripinnate fronds with aceae. short linear ultimate segments, bearing a single row of sporangia with an apical annulus (" monangic sori " of Prantl) on either side of the midrib. This type occurs in Rhaetic and Lower Jurassic rocks of England, the Arctic regions, Japan and elsewhere. Ruffordia Goepperti, a Wealden type, and probably a member of the Schizaeaceae, has been re-corded from England, Belgium, and other European countries, and Japan. The Gleicheniaceae appear to have been represented by Triassic species in North America and Europe, and more abundantly in Jurassic, Weal-den, or Lower Cretaceous rocks in Belgium, Greenland, Poland s and elsewhere. Some excep- 1-3, Sporangia enlarged. rhizomes have been found by Dr 4, Single fertile pinnule slightly C Bommer of Brussels in some enlarged. Wealden deposits at Hainaut , Fragment of pinna. in Belgium; but these have not $ Inferior Oolite, England. yet been fully described. The dichotomously-branched fronds of the type represented by several recent species of Gleichenia, e.g. Qlekhen- G. dichotoma, &c., are abundant in Lower Cretaceous Qlekh. plant-beds of Greenland, and suggest that in the latter part of the Mesozoic period the Gleicheniaceae held a position in the vegetation of the far north similar to that which they now occupy in the southern tropics of India and other regions. The recent Malayan genus Matonia (Map B, Matonia), represented by two species, M. pectinata and M. sarmentosa, is clearly a survival in southern latitudes of a family which occupied Matoni- an important neae. place in the vegetation of the Rhaetic Jurassic and Wealden periods. The genera Lacopteris and Matonidium (fig. 8) may be cited as the two most important types, both as regards geographical and geological range, of this Mesozoic family; these ferns are recorded from England, France, Belgium, Germany, Austria, Portugal, Poland and Italy (Map B, MI), also from Greenland (Map B, M2), Spitsbergen (Map B, M3), and Persia (Map B, M'). From the southern Hemisphere, on the other hand, we know of one or two fragments only which can reasonably be referred to the Matonineae (Map B, M5), a fact which may point to a northern origin for this family with its two surviving species almost confined to the Malayan region. The recent genus, Dipteris, with its four existing species, occurring chiefly in the Indo-Malayan region (Map B, Dipteris), is also a modern survival of several Mesozoic types represented Didiptptee.d by such genera as Dictyophyllum (fig. 9), Hausmannia and Camptopteris, which were abundant during the 'Rhaetic and Jurassic periods in England, Germany, Sweden andelsewhere in Europe (Map B, D). Important additions to our knowledge of the fertile leaves and rhizomes of certain Rhaetic species of Dictyophyllum and other genera have recently been made by Professor Nathorst of Stockholm, and Professor Richter of Quedlinburg has made a thorough investigation of the vegetative organs of Hausmannia, a genus possibly identical with Protorhipis, which is abundant in Lower Cretaceous and other strata in various European localities. The Dip- teridinae are represented also by species from Mesozoic rocks of Persia (Map B, D2), Green-land (Map B, Da), North America (D4), South America (D5) and China (D5). The Cyatheaceae constitute another family of leptospor- angiate Ferns which had several Cyathearepresentatives in ceae. Mesozoic floras. The numerous species of fronds from Jurassic and Wealden rocks of North America and Europe referred to Thyrsopteris, a recent monotypic genus con-fined to Juan Fernandez, are in the majority of cases founded on sterile leaves, and of little or no botanical value. On the other hand, there are several fossil Ferns of Jurassic age possessing cup-like sori like those of Thyrsopteris and other Cyatheaceous Ferns, which indicate a wide Mesozoic distribution for this family. Among Jurassic species which should probably be classed as Cyatheaceae, Coniopteris hymenophylloides is recorded from England, France, Russia, Poland, Bornholm, Italy, the Arctic regions, North America, Japan, China, Australia and India. A few tree-ferns which may be included in this family—'such as Protopteris—have been described from Wealden and Lower Cretaceous rocks of England, Germany and Austria. It is by no means easy in dealing with fossil ferns to distinguish between certain Polypodiaceae—such as species of Davallia—and members of the Cyatheaceae. It is a striking fact that among the numerous Mesozoic Ferns there are comparatively few that can with good reason be referred to the Polypodiaceae, a family which plays so dominant poly-a role at the present day. The frequent occurrence of podiaceae. such names as Asplenium, Adiantum, Davallia, and other Polypodiaceous genera in lists of fossil ferns is thoroughly misleading. There are, indeed, a certain number of species which show traces of sori like those of modern species of Asplenium and other genera, but in most cases the names of recent ferns have been used on insufficient grounds. The Wealden and Jurassic genus, Onychicpsis of England, Portugal, Belgium, Germany, Japan, South Africa and Australia, bears a close resemblance to the recent Onychium (Cryptogamme). Other Jurassic Ferns described by Raciborski from Poland suggest a comparison with Davallia. The resemblance of the sporocarp-like bodies — discovered by Nathorst in association with Rhaetic Sagenopteris leaves, and more recently figured by Halle under a new generic name (Hydropterangium)—to the sporocarps of Marsilia is an argument in favour of including Sagenopteris in the Hydropterideae. The majority of the specimens included in the genus Cladophlebis, the Mesozoic representative of the Palaeozoic Pecopteris type of frond, are known only in a sterile condition, and cannot be assigned to their family position. A Wealden plant, Weichselia Mantelli, is worthy of mention as a species of very wide geographical distribution, and one of the most characteristic members of the Wealden flora. This type is distinguished by its large bipinnate fronds bearing long and narrow pinnae with close-set pinnules, characterized by the anastomosing secondary veins. No traces of sori have so far been found on the fronds, Similarly, the genus Sagenopteris, characterized by a habit like that of Marsilia, and represented by fronds consisting of a few spreading broadly oval or narrow segments, with anastomosing veins, borne on the apex of a common petiole, is abundant in'rocks ranging from the Rhaetic to the Wealden, but has not so far been satisfactorily placed. The evidence adduced by Nathorst and some other writers is, however, not convincing; until we find well-preserved sporocarps in connection with vegetative fronds we prefer to keep an open mind as regards the position of Sagenopteris. The abundance of Cycadean plants is one of the most striking features of Mesozoic floras. In most cases we have only the evidence of sterile fronds, and this is necessarily unsatisfactory; Cycadales. but the occurrence of numerous stems and fertile shoots demonstrates the wealth of Cycadean plants in many parts of the world, more particularly during the Jurassic and Wealden periods. From Palaeozoic rocks a few fronds have been described, such as Pterophyllum Fayoli, P. Combrayi, Plagiozamites and A, Summit of petiole. B, Fertile pinnules. Inferior Oolite, England. (After Schenk.) Sphenozamites, chiefly from French localities, which are referred to fronds, which there is good reason to refer to the Cycadales in the Cycads because of their similarity to the pinnate fronds of Upper Triassic, Rhaetic, Jurassic and Wealden rocks in India, modern Cycadaceae. In the succeeding Triassic system Cycadean Australia, Japan, China and elsewhere in the southern hemisphere, •o~^~~~ LS~tF=7~I1. ~li!~)!=!•iL~t' . 7~~1'I.ft?' on.c, --_-: Via: tel. ^~~ iJ!EI11UIILJ mm gins s' 111:6:;, t IIiIiflPII $1I s- A 1 ~~f~~~ ~ ~M~~. nr 'WM usoo.01M kim. ~~1 II II 101.^Oo :
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