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.)
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| Fig. 7.—Klukia exilis. |
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1-3, Sporangia enlarged. |
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4, Single fertile pinnule slightly enlarged. |
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5, Fragment of pinna. Inferior Oolite, England. |
The Schizaeaceae include a widely spread species, originally named Pecopteris exilis, and subsequently placed in a new genus, Klukia Schizaeaceae. (fig. 7), which is characterized by tripinnate fronds with 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 recorded 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, Wealden, or Lower Cretaceous rocks in Belgium, Greenland, Poland and elsewhere. Some exceptionally perfect fragments of rhizomes have been found by Dr C. Bommer of Brussels in some Wealden deposits at Hainaut in Belgium; but these have not yet been fully described. The dichotomously-branched fronds of the type represented by several recent species of Gleichenia, e.g. Gleicheniaceae. G. dichotoma, &c., are abundant in Lower Cretaceous 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.
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| Fig. 8.—Matonidium Goepperti. |
| A. Summit of petiole. |
| B, Fertile pinnules. |
| Inferior Oolite, England. |
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 Matonineae. an important place in the vegetation of the Rhaetic, Jurassic and Wealden periods. The genera Lacopterisand 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, M1), also from Greenland (Map B, M2), Spitsbergen (Map B, M3), and Persia (Map B, M4). 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 Dipteridinae. modern survival of several Mesozoic types represented by such genera as Dictyophyllum (fig. 9), Hausmannia and Camptopteris, which were abundant during the Rhaetic and Jurassic periods in England, Germany, Sweden and elsewhere 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 Dipteridinae are represented also by species from Mesozoic rocks of Persia (Map B, D2), Greenland (Map B, D3), North America (D4), South America (D5) and China (D6).
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| (After Schenk.) |
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Fig. 9.—Dictyophyllum. Rhaetic rocks of Europe and Asia. |
The Cyatheaceae constitute another family of Cyatheaceae. leptosporangiate Ferns which had several representatives in Mesozoic floras. The numerous species of fronds from Jurassic and Wealden rocks of North America and Europe referred to Thyrsopteris, a recent monotypic genus confined 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 Polypodiaceae. to the Polypodiaceae, a family which plays so dominant a rôle at the present day. The frequent occurrence of 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, Onychiopsis 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 Cycadales. of sterile fronds, and this is necessarily unsatisfactory; 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
