Chapter XXI: Fossil Ferns (1)

=Osmundaceae.=

From the Culm of Silesia, Stur[761] described impressions of sterile fronds which he named _Todea Lipoldi_ on the ground of the similarity of the finely divided pinnules to those of _Todea superba_ and other filmy species of the genus. The type-specimen of Stur (in the Geological Survey Museum, Vienna) affords no information as to sporangial characters and cannot be accepted as an authentic record of a Lower Carboniferous representative of the family. Another more satisfactory but hardly convincing piece of evidence bearing on the presence of Osmundaceae in pre-Permian floras has been adduced by Renault[762], who described petrified sporangia from the Culm beds of Esnost in France as _Todeopsis primaeva_ (fig. 256, F). These pyriform sporangia are characterised by the presence of a plate of large cells comparable with the subapical group of “annulus” cells in the sporangia of the recent species (fig. 221).

Zeiller[763] has published a figure of some sporangia described by Renault from Autun resembling the Osmundaceous type in having a plate of thick-walled cells instead of a true annulus, but the plate is larger than the group of cells in the recent sporangia, and both sporangia and spores are smaller in the fossil. The sporangia from Carboniferous rocks described by Weiss as _Sturiella_[764] bear some resemblance to those of recent Osmundaceae, but there is no adequate reason for referring them to this family.

The generic name _Pteridotheca_ is employed by Scott as a convenient designation for unassigned petrified sporangia of Palaeozoic age with an annulus and other characters indicating fern-affinity. In the species _P. Butterworthi_[765] the sporangia are characterised by a group of large cells suggesting comparison with the annulus, or what represents the annulus, in Osmundaceae and Marattiaceae. Scott has also described a sporangium from the Coal-Measures containing germinating spores[766]; the structure is similar to that of recent Osmundaceous sporangia, and it is interesting to note that germinating spores have been observed in the recent species _Todea hymenophylloides_[767].

Additional evidence of the same kind is afforded by fertile specimens of a quadripinnate fern with deeply dissected oval-lanceolate pinnules described by Zeiller from the Coal-Measures of Heraclea in Asia Minor as _Kidstonia heracleensis_[768] (fig. 256, E). Carbonised sporangia were found at the base of narrow lobes of the ultimate segments and, as seen in fig. 256, E, the sporangial wall is distinguished by a plate of larger cells occupying a position like that of the “annulus” of recent Osmundaceae. Zeiller regards the sporangia as intermediate between those of Osmundaceae and Schizaeaceae. From the same locality Zeiller describes another frond bearing somewhat similar sporangia as _Sphenopteris_ (_Discopteris_) _Rallii_ (fig. 256, D)[769]: the term _Discopteris_ was instituted by Stur for fertile fronds referred by him to the Marattiaceae[770].

It is by no means safe to assume that these and such Upper Carboniferous sporangia as Bower[771] compared with those of _Todea_ were borne on plants possessing the anatomical characters of Osmundaceae rather than those of the extinct Palaeozoic family Botryopterideae. This brings us to the important fact, first pointed out by Renault, that the Botryopterideae are essentially generalised ferns exhibiting many points of contact with the Osmundaceae[772]. It is clear that whether or not we are justified in tracing the Osmundaceae as far back as the Lower Carboniferous period, some of the characteristics of the family were already foreshadowed in rocks of this age.

Through a fortunate accident of preservation, unequivocal evidence of the existence of Osmundaceae in the Palaeozoic era is supplied by the Russian Upper Permian genera _Zalesskya_ and _Thamnopteris_.

_Zalesskya._

This generic title has been instituted by Kidston and Gwynne-Vaughan[773] for two Russian stems of Upper Permian age, one of which was named by Eichwald[774] _Chelepteris gracilis_, but the probability that the type of the genus _Chelepteris_ is generically distinct from Eichwald’s species necessitated a new designation for the Permian fern.

In habit the stem of _Zalesskya_ resembles that of an _Osmunda_ or a _Todea_, but it differs in the possession of a stele composed of a continuous cylinder or solid column of xylem surrounded by phloem, and by the differentiation of the xylem into two concentric zones. The leaves are represented by petiole-bases only; the sporangia are unknown. The stem and leaf-base anatomy fully justifies the inclusion of _Zalesskya_ in the Osmundaceae.

_Zalesskya gracilis_ (Eichwald). Fig. 248.

The type-specimen is a partially decorticated stem, from Upper Permian beds in Russia, provided with a single stele, 13 mm. in diameter, surrounded by a broad thin-walled inner cortex containing numerous leaf-traces and occasional roots: this was doubtless succeeded by a sclerotic outer cortex. In its main features _Zalesskya gracilis_ agrees closely with _Z. diploxylon_ represented in fig. 249. The stele consists of a continuous cylinder of xylem exhibiting a fairly distinct differentiation into two zones, (i) a broader outer zone of narrower scalariform tracheae (_x ii_, fig. 248) in which 20 to 25 protoxylem strands (_px_) occur just within the edge, (ii) an inner zone of broader and shorter tracheae (fig. 248, _x i_). The protoxylem elements (_px_, fig. 248) are characterised by a single series of scalariform pits, while the metaxylem elements have multiseriate pits like those on the water-conducting elements of recent Osmundaceae. The tracheae show an interesting histological character in the absence of the middle substance of their walls, a feature recognised by Gwynne-Vaughan[775] in many recent ferns. External to the xylem and separated from it by a parenchymatous sheath is a ring of phloem, _ph_, composed of large sieve-tubes and parenchyma separated from the inner cortex by a pericycle 4 to 5 layers in breadth. The occurrence of a few sclerotic cells beyond the broad inner cortex points to the former existence of a thick-walled outer cortex. The leaf-traces are given off as mesarch strands from the edge of the xylem; they begin as prominences opposite the protoxylem and become gradually detached as xylem bundles, at first oblong in transverse section, then assuming a slightly crescentic and reniform shape, while the mesarch protoxylem strand takes up an endarch position. As a trace passes further out the curvature increases and the protoxylem strands undergo repeated bifurcation; it assumes in fact the form and general type of structure met with in the leaf-traces of _Todea_ and _Osmunda_. Numerous diarch roots, given off from the stele at points just below the outgoing leaf-traces, pass outwards in a sinuous horizontal course through the cortex of the stem.

In _Zalesskya gracilis_ the xylem cylinder was probably wider in the living plant than in the petrified stem. In _Zalesskya diploxylon_[776], in all probability from the same Russian locality, there can be little doubt that the xylem was originally solid to the centre (fig. 249). In this species also the phloem forms a continuous band (_ph_, fig. 249) consisting of four to six layers of sieve-tubes.

_Thamnopteris_.

_Thamnopteris Schlechtendalii_ (Eich.). Figs. 250, 312, A, Frontispiece.

In 1849 Brongniart[777] proposed the name _Thamnopteris_ for a species of fern from the Upper Permian of Russia originally described by Eichwald as _Anomopteris Schlechtendalii_. A new name was employed by Brongniart on the ground that the fossil was not generically identical with the species previously named by him _Anomopteris Mougeotii_[778]. Eichwald’s specimen has been thoroughly investigated by Kidston and Gwynne-Vaughan[779]. The stem (Frontispiece) agrees in habit with those of _Zalesskya_ and recent Osmundaceae; on the exposed leaf-bases the action of the weather has etched out the horse-shoe form of the vascular strands and laid bare numerous branched roots boring their way through the petiole stumps. The centre of the stem is occupied by a protostele 13 mm. in diameter consisting of solid xylem separated by a parenchymatous sheath from a cylinder of phloem. The xylem is composed mainly of an axial column of short and broad reticulately pitted tracheae (fig. 250, _b_ and Frontispiece), distinguished from the sharply contrasted peripheral zone of normal scalariform elements, _a_, by their thinner walls and more irregular shape. The protoxylem, _px_, is represented by groups of narrower elements rather deeply immersed in the peripheral part of the metaxylem. A many-layered pericycle, _per_, and traces of an endodermis, _en_, succeed the phloem, _ph_, which is characterised by several rows of large contiguous sieve-tubes; beyond the endodermis is a broad thin-walled inner cortex. The leaf-traces arise as in _Zalesskya_, but the protoxylem in _Thamnopteris_ is at first central; as the trace passes outwards a group of parenchyma appears immediately internal to the protoxylem elements and gradually assumes the form of a bay of thin-walled tissue on the inner concave face of the curved xylem. The next stage is the repeated division of the protoxylem strand until, in the sclerotic outer cortex, the traces acquire the Osmundaceous structure (fig. 312, A, p. 453). The petiole bases have stipular wings as in _Todea_ and _Osmunda_.

[Sidenote: OSMUNDACEAE]

The striking feature exhibited by these Permian plants is the structure of the protostele, which in _Thamnopteris_ and probably in _Zalesskya diploxylon_ consists of solid xylem surrounded by phloem: this may be regarded as the primitive form of the Osmundaceous stele. In _Osmunda regalis_ and in other recent species of the genus the xylem cylinder has the form of a lattice-work; in other words, the departure of each leaf-trace makes a gap in the xylem and the overlapping of the foliar-gaps results in the separation of the xylem into a number of distinct bundles. In _Zalesskya gracilis_ the continuity of the xylem is not broken by overlapping gaps; in this it agrees with _Lepidodendron_. In _Thamnopteris_ the centre of the stele was occupied by a peculiar form of xylem obviously ill-adapted for conduction, but probably serving for water-storage and comparable with the short and broad tracheae in _Megaloxylon_[780]. There is clearly a well-marked difference in stelar anatomy between these two Permian genera and _Todea_ and _Osmunda_: this difference appears less when viewed in the light of the facts revealed by a study of the Jurassic species _Osmundites Dunlopi_.

As possible examples of Triassic Osmundaceae reference may be made to some species included in Stur’s genus _Speirocarpus_[781]. _S. virginiensis_ was originally described by Fontaine[782] from the Upper Triassic rocks of Virginia as _Lonchopteris virginiensis_ (fig. 251) and has recently been figured by Leuthardt[783] from the Keuper of Basel. The sporangia, which are scattered over the lower surface of the pinnules, are described as globose-elliptical and as having a rudimentary apical annulus; no figures have been published. In habit the frond agrees with _Todites Williamsoni_, but the lateral veins form an anastomosing system like that in the Palaeozoic genus _Lonchopteris_ (fig. 290, B). There would seem to be an _a priori_ probability of this species being a representative of the Osmundaceae and not, as Stur believed, of the Marattiaceae. Seeing that _Lonchopteris_ is a designation of a purely provisional kind, it would be convenient to institute a new generic name for Triassic species having the Lonchopteris venation, which there are good reasons for regarding as Osmundaceous ferns.

Similarly _Speirocarpus tenuifolius_ (Emmons) (= _Acrostichites tenuifolius_ Font.), which resembles _Todites Williamsoni_ (see p. 339) not only in habit and in the distribution of the sporangia but also in the venation, is probably an Osmundaceous species.

_Osmundites._

_Osmundites Dunlopi_, Kidston and Gwynne-Vaughan[784], fig. 252.

This species was found in Jurassic rocks in the Otago district of New Zealand in association with _Cladophlebis denticulata_[785] (fig. 257). The type-specimen forms part of a stem 17 mm. in diameter surrounded by a broad mass of crowded leaf-bases. The stele consists of an almost continuous xylem ring (fig. 252) enclosing a wide pith: the phloem and inner cortex are not preserved but the peripheral region of the stem is occupied by a sclerotic outer cortex. The mass of encasing leaf-bases resolves itself on closer inspection into zones of foliage-leaf petioles and the petioles of scale-leaves with an aborted lamina. A similar association of two forms of leaf is seen in the existing American species _Osmunda Claytoniana_ and _O. cinnamomea_. The cortex and armour of leaf-bases are penetrated by numerous diarch roots. The xylem cylinder, six to seven tracheae broad, is characterised by the narrower diameter of its innermost elements and—an important point—by the fact that the detachment of a leaf-trace does not break the continuity of the xylem cylinder (fig. 252). Each leaf-trace is at first elliptical in section; it then becomes curved inwards and gradually assumes the horse-shoe form as in _Zalesskya_ and in the recent species. The single endarch protoxylem becomes subdivided until in the petiole it is represented by 20 or more strands.

In the continuity of the xylem cylinder this species of _Osmundites_ shows a closer approach to _Todea barbara_ or _T. superba_ (fig. 221, B) than to species of _Osmunda_; it differs from _Zalesskya_ in having reached a further stage in the reduction of a solid protostele to one composed of a xylem cylinder enclosing a pith. This difference is of the same kind as that which distinguishes the stele of _Lepidodendron rhodumnense_ from _L. Harcourtii_. In _Lepidodendron_ short tracheae occasionally occur on the inner edge of the xylem cylinder, and in recent species of _Todea_ the same kind of reduced tracheae are met with on the inner edge of the xylem[786]. In both cases the short tracheae are probably vestiges of an axial strand of conducting elements which in the course of evolution have been converted into parenchymatous cells. In _Lepidodendron vasculare_ the mixed parenchyma and short tracheae in the centre of the stele represent an intermediate stage in xylem reduction, and the arrangement in vertical rows of the medullary parenchyma in _Lepidodendron_ is precisely similar to that described by Kidston and Gwynne-Vaughan in _Thamnopteris_. In both cases the rows of superposed short cells have probably been produced by the transverse septation of cells which began by elongating as if to form conducting tubes and ended by assuming the form of vertical series of parenchymatous elements.

In another Jurassic species, _Osmundites Gibbiana_[787], the xylem is of the _Osmunda_ type and consists of about 20 strands instead of a continuous or almost continuous cylinder.

_Osmundites Kolbei_ Seward, figs. 253–255.

This species was founded on a specimen obtained by Mr Kolbe from the Uitenhage series of Cape Colony[788]. The fossil flora and fauna of this series point to its correlation with the Wealden or Neocomian strata of Europe[789]. The type-specimen consists of several pieces of a stem (fig. 253) which reached a length of about 90 cm. On the weathered surface the remains of petiole-bases are clearly seen and on the reverse side of the smaller piece shown in the figure numerous sinuous roots are present in association with the leaf-stalks. The depression _c_ in the larger specimen may mark the position of a branch: at _a_ fig. 253 (enlarged in fig. 254, _a_) the vascular strand of a petiole is exposed as a broad =U=-shaped band and at _b_ (fig. 254, _b_) the form of the petiole-bases is clearly shown[790]. With the stem were found imperfectly preserved impressions of fronds referred to _Cladophlebis denticulata_, a common type of leaf which was found also in association with the slightly older New Zealand stem, _Osmundites Dunlopi_.

An examination of the internal structure of the South African stem by Dr Kidston and Mr Gwynne-Vaughan has revealed many interesting features, which will be fully described in Part IV. of their Monograph on fossil Osmundaceous stems. I am greatly indebted to these authors for allowing me to publish the following note contributed by Dr Kidston:—

“The section of _Osmundites Kolbei_ Seward, shown in fig. 255, presents the usual appearance of an Osmundaceous stock. The parts contained in this section are the stele, inner and outer cortex and a portion of the surrounding mantle of concrescent leaf-bases. The whole specimen has suffered much from pressure, but if restored to its original form the xylem ring must have been about 19 mm. in diameter. The number of xylem strands is about fifty-six and several of them are more or less joined as in the modern genus _Todea_. The tracheae are of the typical Osmundaceous type, that is to say, the pits are actual perforations and several series of them occur on each wall of the larger tracheae.

“The most interesting structural characteristic of _Osmundites Kolbei_ is not well seen in the figure owing to the compression of the xylem ring. This consists in the occurrence of tracheae in the pith. In fact, we have here a mixed pith, composed of parenchyma and true tracheae, a condition which connects the _Osmundaceae_ with a parenchymatous medulla with those possessing a solid xylem stele like _Zalesskya_ and _Thamnopteris_ and so completes the series of transitions extending from the older and solid-steled forms to the modern medullated members of the _Osmundaceae_.”

_Osmundites skidegatensis_, Penhallow.

This lower Cretaceous Canadian species, first described by Penhallow[791] and more recently by Kidston and Gwynne-Vaughan[792], is remarkable for the large size of the stem, the stele alone having a diameter of 2·4 cm. Penhallow figures a fragment of a leaf bearing a superficial resemblance to that of _Osmunda Claytoniana_, which may be the foliage borne by _Osmundites skidegatensis_. The xylem cylinder is broken by the exit of leaf-traces into 50 or more strands varying in size and shape, and it is noteworthy that the phloem is also interrupted as each leaf-trace is given off. In recent species the xylem cylinder is almost always interrupted, but the phloem retains its continuity. In the Canadian fossil an internal band of phloem occurs between the xylem and the pith, and this joins the external phloem at each leaf-gap. This internal phloem finds an interesting parallel in certain recent species[793], but in these the internal and external phloem do not meet at the foliar gaps as they do in the extinct type. In _Osmunda cinnamomea_ the internal phloem occurs only at the regions of branching of the stem stele; in the fossil it is always present.

It is clear that _Osmundites skidegatensis_ represents the most complex type of stem so far recognised in the Osmundaceae; it illustrates a stage in elaboration of the primitive protostele in advance of that reached by any existing species.

• • • • •

The primitive Osmundaceous stele was composed of solid xylem surrounded by phloem (_Thamnopteris_ and _Zalesskya_); at a later stage the xylem cylinder lost its inner zone of wide and short tracheae and assumed the form seen in _Osmundites Kolbei_, in which the centre of the stele consists of parenchyma with some tracheae. Another type is represented by _O. Dowkeri_ in which the pith is composed wholly of parenchyma and the xylem ring is continuous. From this type, by expansion of the xylem ring and by the formation of overlapping leaf-gaps, the form represented by _Osmunda regalis_ was reached. _Osmunda cinnamomea_, with internal phloem in the regions of stelar branching, probably represents a further stage, as Kidston and Gwynne-Vaughan believe, in increasing complexity due to the introduction of phloem from without through gaps produced by the branching of the stele. In _Osmundites skidegatensis_ the leaf-gaps became wider and the external phloem projected deeper into the stele until a continuous internal phloem zone was produced. This most elaborate type proved less successful than the simpler forms which still survive.

_Osmundites Sturii._

Impressions of fertile pinnae with narrow linear segments bearing exannulate sporangia described by Raciborski from Lower Jurassic rocks in Poland as _Osmunda Sturii_[794] may with some hesitation be included in the list of Mesozoic Osmundaceae.

_Osmundites Dowkeri._

Under this name Carruthers[795] described a petrified stem from Lower Eocene beds at Herne Bay, which in the structure of the stele agrees closely with the Jurassic species _O. Gibbiana_ and conforms to the normal Osmundaceous type. It is possible, as Gardner and Ettingshausen[796] suggested, that the foliage of this species may be represented by some sterile _Osmunda_-like fragments recorded from the Middle Bagshot beds of Bovey Tracey and Bournemouth as _Osmunda lignitum_.

_Todites._

This generic name[797] has been applied to fossil ferns exhibiting in the structure of the sporangia and in the general habit of the fertile fronds a close resemblance to the recent species _Todea barbara_ (fig. 221, D, p. 286).

_Todites Williamsoni_ (Brongniart) figs. 256, B, C, G.

1828. _Pecopteris Williamsonis_, Brongniart, Prodrome, p. 57; Hist.
vég. foss., p. 324, Pl. CX. figs. 1 and 2.

—— _P. whitbiensis_, Brongniart, Hist. vég. foss. p. 321, Pl. CIX.
figs. 2–4.

—— _P. tenuis_, _ibid._ p. 322, Pl. CX. figs. 3, 4.

1829. _Pecopteris recentior_, Phillips, Geol. Yorks. p. 148, Pl.
VIII. fig. 15.

—— _P. curtata_, _ibid_. Pl. VIII. fig. 12.

1833. _Neuropteris recentior_, Lindley and Hutton, Foss. Flora, Vol.
I. Pl. LXVIII.

—— _Pecopteris dentata_, _ibid._ Vol. III., Pl. CLXIX.

1836. _Acrostichites Williamsonis_, Goeppert, foss. Farn. p. 285.

1841. _Neuropteris Goeppertiana_, Muenster, in Goeppert, Gattungen
foss. Pflanz. Lief. 5 and 6, p. 104, Pls. VIII.–X.

1856. _Pecopteris Huttoniana_, Zigno, Flor. foss. Oolit. Vol. I. p.
133.

1867. _Acrostichites Goeppertianus_, Schenk, Foss. Flor. Grenzsch. p.
44, Pl. V. fig. 5, Pl. VII. fig. 2.

1883. _A. linnaeaefolius_, Fontaine, Older Mesoz. Flora Virginia, p.
25, Pls. VI.–IX.

— _A. rhombifolius_, _ibid_. Pls. VIII. XI.–XIV.

1885. _Todea Williamsonis_, Schenk, Palaeont. Vol. XXXI. p. 168, Pl.
III. fig. 3.

1889. _Cladophlebis virginiensis_, Fontaine, Potomac Flora, p. 70,
Pl. III. figs. 3–8; Pl. IV. figs. 1, 4.

A. _Cladophlebis denticulata._
B, B′. _Todites Williamsoni_ (fertile).
C. _T. Williamsoni_ (sterile pinna).
D. _Discopteris Rallii._
E, E′. _Kidstonia heracleensis._
F. _Todeopsis primaeva._
G. _Todites Williamsoni_ (sporangium).

[B, C, from specimens (13491; 39234) in the British Museum (B,
very slightly reduced; C, ½ nat. size); D, E, after Zeiller; F,
after Renault; G, after Raciborski.]]

It is hopeless to attempt to arrive at satisfactory conclusions in regard to the applicability of the name _Todites Williamsoni_ to the numerous fronds from Jurassic and Rhaetic rocks, agreeing more or less closely with Brongniart’s type-specimen. Specimens from the Rhaetic may not be specifically identical with those from the Jurassic; the main point is that, whether actually identical or not, both sets of fossils clearly represent the same general type of Osmundaceous fern[798] and may for present purposes be included under the same designation. The above synonymy, though by no means complete[799], serves to illustrate the confusion which has existed in regard to this widely spread type of Mesozoic fern.

_Todites Williamsoni_ may be briefly described as follows:—

Frond bipinnate; long linear pinnae (20–30 cm.) of uniform breadth
arise at an acute angle, or in the lower part of a frond, almost at
right angles, from a stout rachis. Closely set pinnules attached
by a broad base; slightly falcate, the side towards the rachis
strongly convex and the outer margin straight or concave and
bulged outwards towards the base of each segment, margin usually
entire, or it may be slightly lobed. Fertile pinnules similar to
the sterile; sporangia of the Osmundaceous type and often scattered
over the whole lower surface of the lamina (fig. 256, B, B′, G).
Venation of the _Cladophlebis_ type (cf. fig. 256, A).

It is not always easy to distinguish _Todites Williamsoni_ from _Cladophlebis denticulata_, another common Jurassic fern, but in the latter the pinnules are usually longer and relatively narrower and the rachis is more slender (cf. fig. 256, B and 257). Schenk[800] and Raciborski[801] have shown that the sporangia of _Todites_ conform in the absence of a true annulus to those of _Todea_ (fig. 256, G) and _Osmunda_. Nathorst[802] has recently figured a group of spores of _Todites Williamsoni_ in illustration of the use of the treatment of carbonised impressions with nitric acid and potassium chlorate. This species, though widely distributed in Jurassic rocks, is hardly distinguishable from the German Rhaetic fronds figured by Schenk from Bayreuth as _Acrostichites Goeppertianus_[803], or from other fossils referred to an unnecessarily large number of species by Fontaine[804] from Upper Triassic rocks of Virginia[805].

It would seem from the paucity of later records of Osmundaceae that the family reached its zenith in the Jurassic era. When we pass to the later Tertiary and more recent deposits evidence is afforded in regard to the geographical range of _Osmunda regalis_. It has been shown to occur in the Pliocene forest-bed of Norfolk[806] as well as in Palaeolithic and Neolithic deposits[807].

A fertile frond from the Molteno (Rhaetic) beds of South Africa referred to _Cladophlebis_ (_Todites_) _Roesserti_ (Presl)[808] represents in all probability an Osmundaceous fern closely allied to _Todites Williamsoni_. The same species is described by Zeiller[809] from Rhaetic rocks of Tonkin and very similar types are figured by Leuthardt[810] from Upper Triassic rocks of Basel as _Pecopteris Rutimeyeri_ Heer, and by Fontaine[811] from rocks of the same age in Virginia.

_Cladophlebis._

The generic name _Cladophlebis_ was instituted by Brongniart for Mesozoic fern fronds characterised by ultimate segments of linear or more or less falcate form attached to the pinnae by the whole of the base, as in the Palaeozoic genus _Pecopteris_, possessing a midrib strongly marked at the base and dividing towards the distal end of the lamina into finer branches and giving off secondary forked and arched veins at an acute angle. The term is generally restricted to Mesozoic fern fronds which, on account of the absence or imperfection of fertile pinnae, cannot be safely assigned to a particular family. In the case of the species described below, the evidence in regard to systematic position, though not conclusive, is sufficiently strong to justify its inclusion in the Osmundaceae.

_Cladophlebis denticulata_ Brongniart. Figs. 256, A; 257, 258.

1828. _Pecopteris denticulata_[812], Brongniart, Prodrome, p. 57;
Hist. vég. foss. p. 301, Pl. XCVIII. figs. 1, 2.

— _P. Phillipsii_, Brongniart, Hist. p. 304, Pl. CIX. fig. 1.

This species is often confused[813] with _Todites Williamsoni_. The name _Pecopteris whitbiensis_ has been used by different writers for Jurassic fronds which are undoubtedly specifically distinct: specimens so named by Brongniart should be referred to _Todites Williamsoni_, while _P. whitbiensis_ of Lindley and Hutton[814] is Brongniart’s _Cladophlebis denticulata_. It is impossible to determine with accuracy the numerous examples described as _Pecopteris whitbiensis_, _Asplenium whitbiense_, _Cladophlebis Albertsii_ (a Wealden species[815]), _Asplenium_, or _Cladophlebis_, _nebbense_[816], etc., from Jurassic and Rhaetic strata. The _Cladophlebis denticulata_ form of frond is one of the commonest in recent ferns; it is represented by such species as _Onoclea Struthopteris_, _Pteris arguta_, _Sadleria sp._, _Gleichenia dubia_, _Alsophila lunulata_, _Cyathea dealbata_, and species of _Polypodium_. It is, therefore, not surprising to find records of this Mesozoic species from many localities and horizons. All that we can do is to point out what appear to be the most probable cases of identity among the numerous examples of fronds of this type from Mesozoic rocks, particularly Rhaetic and Jurassic, in different parts of the world. The name _Cladophlebis denticulata_ may be employed in a comprehensive sense for fronds showing the following characters:—

Leaf large, bipinnate, with long spreading pinnae borne on a
comparatively slender rachis. Pinnules, in nearly all cases,
sterile, reaching a length of 3–4cm., acutely pointed, finely
denticulate or entire, attached by the whole of the base (fig.
257). In the apical region the pinnules become shorter and broader.
Venation of the _Cladophlebis_ type (fig. 256, A). Fertile pinnules
rather straighter than the sterile, characterised by linear sori
parallel to the lateral veins (fig. 258).

In endeavouring to distinguish specifically between fronds showing a general agreement in habit with _C. denticulata_, special attention should be paid to venation characters, the shape of the pinnules, the relation of the two edges of the lamina to one another, and to the amount of curvature of the whole pinnule. Unless the material is abundant, it is often impossible to distinguish between characters of specific value and others which are the expression of differences in age or of position on a large frond, to say nothing of the well-known variability which is amply illustrated by recent ferns. It is remarkable that very few specimens are known which throw any light on the nature of the fertile pinnae. Fig. 258 represents an impression from the Inferior Oolite rocks of the Yorkshire coast in which the exposed upper surface of the pinnules shows a series of parallel ridges following the course of the lateral veins and no doubt formed by oblong sori on the lower surface. There can be little doubt that the specimen figured by Lindley and Hutton and by others as _Pecopteris undans_[817] is, as Nathorst suggests, a portion of a fertile frond of _C. denticulata_. A fertile specimen of a frond resembling in habit _C. denticulata_, which Fontaine has described from the Jurassic rocks of Oregon as _Danaeopsis Storrsii_[818], exhibits, as that author points out, a superficial resemblance to the specimen named by Lindley and Hutton _Pecopteris undans_. There is, however, no adequate reason for referring the American fragment to the Marattiaceae. In the absence of sporangia we cannot speak confidently as to the systematic position of this common type; but there are fairly good grounds for the assertion that some at least of the fronds described under this name are those of Osmundaceae. The English specimen shown in fig. 258 is very similar to some Indian fossils figured by Feistmantel as _Asplenites macrocarpus_[819], which are probably identical with _Pecopteris australis_ Morris[820], a fern that is indistinguishable from _Cladophlebis denticulata_. Renault[821] figured a fertile specimen of the Australian fossil as _Todea australis_, which agrees very closely with that shown in fig. 258, and the sporangia figured by the French author are of the Osmundaceous type. Another example of a fertile specimen is afforded by a Rhaetic fern from Franconia, _Asplenites ottonis_, which is probably identical with _Alethopteris Roesserti_ Presl [= _Cladophlebis_ (_Todites_) _Roesserti_], a plant closely resembling _Cladophlebis denticulata_. Another argument in favour of including _C. denticulata_ in the Osmundaceae is supplied by the association of pinnae of this type with the petrified stem of _Osmundites Dunlopi_ recorded by Kidston and Gwynne-Vaughan.

=Schizaeaceae.=

Evidence bearing on the existence of this family in Carboniferous floras is by no means decisive. The generic name _Aneimites_ proposed by Dawson[822] for some Devonian Canadian plants resembling species of the recent genus _Aneimia_, and adopted by White[823] for a species from the Pottsville beds of Virginia, is misleading. The Canadian plants give no indication of the nature of the reproductive organs, and the fronds described by White are, as he shows, those of a Pteridosperm and bore seeds.

An examination of the suspiciously diagrammatic drawings published by Corda[824] of the small fertile pinnules of a Carboniferous fern from Bohemia, which he named _Senftenbergia elegans_, leads us to conclude that the sporangia are almost certainly those of a Schizaeaceous species. The small linear pinnules bear two rows of sessile sporangia, singly as in recent Schizaeaceae and not in sori, characterised by 4–5 rows of regular annular cells (fig. 270, A) surrounding the apex. It has already been pointed out that the apical annulus of recent Schizaeaceae, though normally one row deep, may consist in part at least of two rows. Zeiller[825] examined specimens of Corda’s species and decided in favour of a Schizaeaceous affinity; he describes the sporangia as 0·85–0·95 mm. in length, with 3 to 5 and occasionally only two rows of cells in the apical annulus. Zeiller’s figures (fig. 270, A) confirm the impression that Corda’s drawings are more beautiful than accurate. Stur[826], on the other hand, who first pointed out that the type-specimens of _Senftenbergia_ came from the Radnitz beds of Bohemia and not from the Coal-Measures, convinced himself that the sporangia have no true annulus (fig. 270, E). He describes them as characterised by a comparatively strong wall and by the presence of a band of narrow vertical cells marking the line of dehiscence, features which lead him to assign the plant to the Marattiales, a group which seems to have exercised a dominating influence over his judgment. In a later publication Zeiller[827] replies to Stur’s criticism but adheres to his original opinion. Solms-Laubach[828], while expressing himself in favour of Marattiaceous affinity, recognises that Zeiller’s arguments cannot be set aside.

The question must remain open until further evidence is forthcoming; but it would seem that this Carboniferous type, not as yet recognised in Britain, possessed sporangia having a distinct resemblance to those of the Schizaeaceae, though this similarity does not amount to proof of the existence of the family in the Palaeozoic era.

Palaeozoic floras may be described as rich in generalised types, types foreshadowing lines of evolution, which in the course of ages led to a sorting and a redistribution of characters. It may be that _Senftenbergia_ is one of these generalised types.

• • • • •

It is not until we ascend the geological series as far as the older Jurassic rocks that we meet with a type which can with confidence be classed with the Schizaeaceae, as least so far as sporangial characters are concerned. The species _Klukia exilis_ is selected as the best known and most widely-spread representative of Jurassic Schizaeaceae.

_Klukia exilis_ (Phillips)[829]. Fig. 259.

The generic name _Klukia_ was proposed by Raciborski[830] for a species originally described by Phillips[831] from the Inferior Oolite of the Yorkshire coast as _Pecopteris exilis_. Bunbury’s[832] discovery (supplemented by additional evidence obtained by Raciborski) of well-preserved sporangia justified the substitution of a distinctive designation for the provisional term _Pecopteris_.

The species may be defined as follows:—

Frond tripinnate, of the _Cladophlebis_ type; pinnae linear,
lanceolate, attached to the rachis at a wide angle. Ultimate
segments short and linear, entire or, in the lower part of a frond,
crenulate, 5 mm. long or occasionally longer. Sporangia 0·5 mm. in
length, borne singly on the lower surface of the lamina in a row on
each side of the midrib.

A re-examination[833] of the specimen described by Bunbury confirmed his account of the structure of the sporangia. The pinna shown in fig. 259 is characterised by unusually small fertile pinnules some of which bear 10 sporangia in two rows; the annulus includes about 14 cells. Fertile specimens of this and similar forms are figured by Raciborski[834] from Jurassic rocks of Poland, and good examples of the English species may be seen in the Leckenby collection, Cambridge, in the British Museum, the museums of Manchester, Scarborough, and other places.

It is possible that specimens referred to _K. exilis_ by Yokoyama[835] from Wealden strata in Japan may afford evidence of the persistence of the species beyond the Jurassic era, but in view of the close resemblance of the sterile fronds described from Wealden strata as _Cladophlebis Brownii_[836] and _C. Dunkeri_[836] to those of _Klukia exilis_, identity can be established only by an examination of fertile specimens. A Jurassic fern recently described by Yabe[837] from Korea as _Cladophlebis koraiensis_ may be identical with _K. exilis_ and there is little doubt as to the existence of the species in Jurassic Caucasian strata[838].

_Ruffordia Goepperti_ (Dunk.). Fig. 260.

This Wealden fern[839] has been doubtfully assigned to the Schizaeaceae on the ground of the resemblance of the sterile fronds to those of some species of _Aneimia_, and because of the difference between the sterile and fertile pinnae (Fig. 260). _Ruffordia_ cannot be regarded as a well authenticated member of the Schizaeaceae.

A, A′. _Chrysodium lanzaeanum._
B, B′. _Lygodium Kaulfussi._
C. _Marattia Hookeri._

(After Gardner and Ettingshausen; A, B, ¾ nat. size.)]

_Lygodium Kaulfussi_, Heer. Fig. 261, B, B′.

Fragments of forked pinnules, agreeing very closely in venation and general appearance with recent species of _Lygodium_, have been identified by Gardner and Ettingshausen[840] from English Eocene beds and by Knowlton from the Miocene beds of the Yellowstone Park[841] as _Lygodium Kaulfussi_ Heer (fig. 261, B). Despite the absence of sporangia it is probable that these fragments are correctly referred to the Schizaeaceae. The sterile and fertile specimens figured by Heer[842] from Tertiary beds of Switzerland agree very closely with recent examples of _Lygodium_. Similar though perhaps less convincing evidence of the existence of this family in Europe is furnished by Saporta[843], who described two Eocene species from France.

=Gleicheniaceae.=

The application by Goeppert[844] and other earlier writers of the generic name _Gleichenites_ to examples of Palaeozoic ferns was not justified by any satisfactory evidence. One of Goeppert’s species, _Gleichenites neuropteroides_, is identical with _Neuropteris heterophylla_[845], a plant now included in the Pteridosperms.

The resemblance of sporangia and sori, whether preserved as carbonised impressions or as petrified material, from Carboniferous rocks, to those of recent species of Gleicheniaceae is in many cases at least the result of misinterpretation of deceptive appearances. Williamson[846] drew attention to the Gleichenia-like structure of some sections of sporangia from the English Coal-Measures, but he did not realise the ease with which sections of Marattiaceous sporangia in different planes may be mistaken for those of annulate (leptosporangiate) sporangia. In the regular dichotomous habit of Carboniferous fronds described as species of _Diplothmema_ (Stur) and _Mariopteris_ (Zeiller)[847] we have a close correspondence with the leaves of _Gleichenia_, but the common occurrence of dichotomous branching among ferns is sufficient reason for regarding this feature as an untrustworthy criterion of relationship. It is, however, interesting to find that in addition to the existence of some Upper Carboniferous ferns with sori like those of recent Gleichenias, the type of stelar anatomy illustrated by _Gleichenia dicarpa_ (fig. 237, C, p. 310) and other species is characteristic of the primary structure of the stem of the Pteridosperm _Heterangium_. We find in Carboniferous types undoubted indications of anatomical and other features which in succeeding ages became the marks of Gleicheniaceae.

Some Carboniferous fronds with short and small pinnules of the _Pecopteris_ type, bearing sori composed of a small number of sporangia, have been assigned by Grand’Eury and other authors to the Gleicheniaceae; the same form of sorus is met with also on fronds with Sphenopteroid segments. The former is illustrated by _Oligocarpia Gutbieri_[848] and the latter by _O. Brongniarti_ described by Stur and by Zeiller[849]. Zeiller has described the circular sori of _Oligocarpia_ (fig. 270, B) as consisting of three to ten pyriform sporangia borne at the ends of lateral veins and possessing a complete transverse annulus, but Stur[850] believes that the annulus-like appearance is due to the manner of preservation of exannulate sporangia. In this opinion Stur is supported by Solms-Laubach[851] and by Schenk[852]. Despite an agreement between _Oligocarpia_ and _Gleichenia_, as regards the form of the sori and the number of sporangia, it is not certain that the existence of a typical Gleicheniaceous annulus has been proved to occur in any Palaeozoic sporangia[853].

From Upper Triassic beds of Virginia, Fontaine has figured several fronds for which he instituted the genus _Mertensides_[854]. The habit, as he points out, is not dichotomous, but the sori are circular and are said to be composed in some species of four to six sporangia. No satisfactory evidence is brought forward in support of the use of a designation implying a close relationship with recent Gleichenias (sect. _Mertensia_). One of the species described by Fontaine was originally named by Bunbury _Pecopteris bullatus_[855], the imperfect type-specimen of which is now in the Museum of the Cambridge Botany School. In the form of the frond, the thick rachis, and in the pinnules this Triassic species resembles _Todites Williamsoni_, but the resemblance does not extend to the sori. Two of Fontaine’s species are recorded by Stur from Austria[856], but he places them in the genus _Oligocarpia_ and includes them in the Marattiaceae.

Leuthardt[857] figures what appears to be a Gleicheniaceous fern from the Upper Triassic beds of Basel as _Gleichenites gracilis_ (Heer) showing sori composed of five sporangia (fig. 265, C) with a horizontal annulus. A Rhaetic species _Gleichenites microphyllus_ Schenk[858] from Franconia agrees in the form of its small rounded pinnules with _Gleichenia_, but no sporangia have so far been found.

An impression of a frond from Jurassic rocks of northern Italy figured by Zigno as _Gleichenites elegans_[859] closely resembles in habit recent species of _Gleichenia_; though no sporangia have been found, the habit of the frond gives probability to Zigno’s determination.

A Jurassic species from Poland, _Gleichenites Rostafinskii_, referred by Raciborski[860] to _Gleichenia_, exhibits a close agreement in habit and in the form of the soral impressions to some recent species of _Gleichenia_.

As we pass upwards to Wealden and more recent rocks it becomes clear that the Gleicheniaceae were prominent members of late Mesozoic floras in north Europe and reached as far north as Disco Island. In English Wealden beds portions of sterile fronds have been found which were assigned to a new genus _Leckenbya_[861], but it is probable that these specimens would be more correctly referred to _Gleichenites_. Similarly fragments of Gleichenia-like pinnae with very small rounded pinnules occur in the Wealden rocks of Bernissart, Belgium[862], in north Germany[863], and elsewhere. Conclusive evidence has been obtained by Prof. Bommer of the existence of _Gleichenites_ in Wealden beds near Brussels, where many plant remains have been found in a wonderful state of preservation. The specimens, which I had an opportunity of seeing some years ago, might easily be mistaken for rather old and brown pieces of recent plants. Some of the Belgian fragments, of which Prof. Bommer has kindly sent me drawings and photographs, are characterised by an arrangement of vascular tissue identical with that in the petioles and rhizomes of some protostelic Gleichenias. The stele of one of the Belgian rhizomes appears to be identical with that of _Gleichenia dicarpa_ (fig. 237, C. p. 310).

A. _Gleichenites longipennis_ Heer.
B. _G. delicatula_ Heer.
C. _G. Nordenskioldi_ Heer.
D. _G. Zippei_. (Corda.)

(After Heer; A, B, D, very slightly reduced.)]

_Gleichenites Zippei_ (Corda). Fig. 262, D.

This species, originally described by Corda as _Pecopteris Zippei_[864] and afterwards figured by Heer[865] as _Gleichenia Zippei_ (fig. 262, D) from Urgonian rocks of Greenland, affords a striking example of a Mesozoic member of the _Gleicheniaceae_. It is characterised by the dichotomous branching of the frond and by the occurrence of arrested buds in the forks. The long and slender pinnae, reaching a length of 9 cm. and a breadth of 6–8 mm., bear small crowded pinnules occasionally with circular sori which are described by Heer as consisting of a small number of sporangia (cf. fig. 262, C). Several other Lower Cretaceous species are recorded by Heer from Greenland, some of which are probably unnecessarily separated from _Gleichenites Zippei_. Examples of these are represented in fig. 262, A, B, C.

A Gleicheniaceous species described by Debey and Ettingshausen from Lower Cretaceous rocks of Aix-la-Chapelle as _Didymosorus comptonifolius_[866] is very similar in habit to some of Heer’s Greenland species: this should probably be referred to the genus _Gleichenites_.

_Gleichenites hantonensis_, Wank. Fig. 263.

From the Eocene beds of Bournemouth, Gardner and Ettingshausen[867] have described under the name _Gleichenia hantonensis_ what is in all probability a true _Gleichenia_ (fig. 263). This species, originally recorded by Wanklyn[868], is characterised by a slender forked rachis showing what may be traces of arrested buds between the arms of the branches, by circular sori of six or eight sporangia and by the presence of peculiar tendril-like appendages on the pinnae. If the description of the tendrils is correct, this British species affords one of the few instances of ferns adapted for climbing and may be compared with the recent species _Davallia aculeata_ (fig. 232, p. 299).

=Matonineae.=

The genera _Laccopteris_ and _Matonidium_ may be described as examples of Mesozoic ferns exhibiting a very close agreement with _Matonia_.

_Laccopteris_. This genus, founded by Presl[869], may be described as follows:—

Frond pedate, in habit resembling _Matonia pectinata_, with
pinnate or pinnatifid pinnae; ultimate segments linear, provided
with a well-marked midrib giving off numerous dichotomously
branched secondary veins which are in places connected by lateral
anastomoses. Sori circular, forming a single row on each side of
the midrib (fig. 278, B); sporangia 5–15 in each sorus, with an
oblique annulus and tetrahedral spores. The presence of an indusium
is not certainly established.

Schenk[870], who described several specimens of _Laccopteris_ from Rhaetic rocks of Germany, compared the genus with _Gleichenia_ but he also recognised the close resemblance to _Matonia pectinata_. Zeiller[871] first established the practical identity of the sori and sporangia of _Laccopteris_ and _Matonia_. The Rhaetic species, such as _L. Muensteri_, _L. elegans_, and _L. Goepperti_, agree very closely with _L. polypodioides_ and need not be described in detail.

The Rhaetic species _Laccopteris elegans_, represented in fig. 264, illustrates the characteristic habit of the genus and shows a feature usually overlooked[872], namely the occurrence of anastomoses between the lateral veins. The form of the sorus of another Rhaetic species is shown in fig. 265, E. Schenk figures an interesting series of fronds of _L. Goepperti_ in different stages of growth[873]; one of the younger leaves is seen in fig. 265, D. An examination of Rhaetic specimens of _Laccopteris_ in the Bergakademie of Berlin convinced me of the correctness of the published descriptions of the sori.

A. _Matonidium Wiesneri._ (Slightly enlarged.)
B. _Marattiopsis marantacea._ (Slightly enlarged.)
C. _Gleichenites gracilis._ (Slightly enlarged.)
D. _Laccopteris Goepperti._ (Slightly reduced.)
E. _L. Muensteri._ (Enlarged.)

(A, after Krasser; B, C, after Leuthardt; D, E, after Schenk.)]

_Laccopteris polypodioides_ (Brongniart). Figs. 266–268; 278, A.

1828. _Phlebopteris polypodioides_[874], Brongniart, Hist. vég. foss.
p. 372, Pl. LXXXIII. fig. 1.

— _P. propinqua_, _ibid._ Pls. CXXXII. fig. 1, CXXXIII. fig. 2.

1829. _Pecopteris caespitosa_, Phillips, Geol. Yorks. p. 148,
Pl. VIII. fig. 10.

— _P. crenifolia_, _ibid._ Pl. VIII. fig. 10.

— _P. ligata_, _ibid._ Pl. VIII. fig. 14.

In habit this species closely resembles _Matonia_ and _Matonidium_, the long petiole divides distally into several spreading pinnatifid pinnae with linear ultimate segments (fig. 278, A). Circular sori (indusiate?) occur in a single row on each side of the midrib containing 12–14 large sporangia (fig. 266) characterised by an obliquely vertical annulus. The midrib of the pinnules gives off secondary veins at a wide angle and these form a series of elongated meshes parallel to the median rib, as in the recent genus _Woodwardia_; forked and anastomosing branches are given off from these to the edge of the lamina (fig. 267).

A, B. From the Inferior Oolite of Yorkshire.
C. From the Inferior Oolite of Stamford. (British Museum.)]

The specimen shown in fig. 268 is probably a young frond of this species.

A very similar, possibly a specifically identical plant, was described by Leckenby from English Jurassic rocks as _Phlebopteris Woodwardi_[875], the distinguishing features of which are the greater number of lateral veins and the smaller sori (fig. 267, A).

The name _Microdictyon_ was proposed by Saporta[876] for pinnules differing slightly from those of _Laccopteris_ in venation characters: he included _Laccopteris Woodwardi_ in this genus, but such differences as are recognisable in the venation hardly justify the use of a distinct generic title. Similarly, specimens described by Debey and Ettingshausen[877] from Lower Cretaceous rocks of Aix-la-Chapelle as species of _Carolopteris_ may also be included in _Laccopteris_.

_Laccopteris Dunkeri_ (Schenk)[878].

This species is represented in several Wealden localities by fragments of fertile pinnae similar to those of _L. polypodioides_. It is almost impossible to distinguish small specimens of the Wealden fern from Heer’s genus _Nathorstia_ (Marattiaceae) unless the sori are well preserved. This species occurs in Wealden beds in England, Germany, Belgium, and elsewhere and has been discovered by Dr Marcus Gunn in Upper Jurassic plant-beds of Sutherlandshire (N.E. Scotland).

• • • • •

_Laccopteris_ is widely spread in Rhaetic, Jurassic and Lower Cretaceous floras. It affords evidence of the former abundance in northern latitudes of a family now represented by the two species of _Matonia_ confined to a restricted area in the southern hemisphere.

_Matonidium._

Schenk[879] instituted this convenient term for fossil fern fronds agreeing in habit and in their sori with _Matonia pectinata_ (figs. 227, 228, p. 292). Zeiller[880] has drawn attention to the fact that the Mesozoic species differ from the surviving types in the greater number of sporangia in each sorus, and, it may be added, in _Matonidium_ the fertile pinnules are more richly supplied with sori than are those of _Matonia_. Unfortunately our knowledge of the structure of the sporangia of _Matonidium_ is less complete than in the case of _Laccopteris_, but such evidence as is available justifies the conclusion that _Matonia_ is a direct descendant of ferns which formed a prominent feature in European Jurassic and Wealden floras. It is interesting to find that in a Cretaceous species, described by Krasser (fig. 265, A) since the publication of Zeiller’s paper, the sori appear to be identical in distribution and in appearance with those of the recent species.

I am indebted to Prof. Bommer for permission to reproduce the unpublished drawing represented in fig. 237 D (p. 310) of a section of the rhizome of _Matonidium_ from the Belgian Wealden beds of Hainaut (“Flore Bernissartienne”). The section shows an arrangement of vascular tissue identical with that in the recent species: there may be two solenosteles and in addition a solid axial strand. The form of the leaf-trace in the fossil appears to be identical with that in _Matonia pectinata_ (fig. 237, A, p. 310).

_Matonidium Goepperti_ (Ettingshausen)[881]. Fig. 269.

Under this name are included specimens from Inferior Oolite and Wealden strata in Britain and elsewhere. It is, however, not impossible that if more information were available, we should find adequate reasons for recognising two specific types. Fontaine[882], adhering rigidly to the rules of priority, speaks of this species as _Matonidium Althausii_ (Dunker), but Ettingshausen’s specific term is better known.

Fronds pedate and apparently identical in habit with those of
_Matonia pectinata_; ultimate segments linear, slightly falcate and
bluntly pointed. Sori circular or oval, numerous, containing 15
to 20 sporangia with an oblique annulus, in two rows on the lower
surface of the pinnules; indusium as in _Matonia_.

The English examples have so far afforded no information in regard to sporangial structure, but Schenk[883] has recognised a distinct annulus in German material. In his description of fossil plants from Lower Cretaceous rocks in California, Fontaine[884] doubtfully identifies two very small fragments as _Matonidium Althausii_; the evidence is, however, wholly inadequate.

_Matonidium Wiesneri_, Krasser[885]. Fig. 265, A.

This Cenomanian (Cretaceous) species from Moravia appears to be identical in habit with the older type. The pinnules are larger and bear fewer sori. Krasser’s figures of the sterile pinnules show no lateral anastomosing between the secondary veins, but the small vascular network below each sorus (fig. 265, A) is identical with that in _Matonia pectinata_. The indusiate sori contain about six sporangia with an oblique annulus.

The very wide geographical distribution of the Matonineae during the Mesozoic era affords a striking contrast to the limited range of the Malayan survivals.

=Hymenophyllaceae.=

The frequent use of the generic name _Hymenophyllites_ as a designation of Palaeozoic ferns, more particularly in the older literature, is another instance of the undue importance which palaeobotanists have always been prone to attach to external resemblances of vegetative organs. The fragment of lamina described by Stur for the Culm Measures of Austria as _Hymenophyllum waldenburgense_[886] has no claim to consideration as evidence of Palaeozoic Hymenophyllaceae. On the other hand, there are a few records of fertile fronds which, though not to be accepted without reserve, are worthy of more careful examination. Some petrified sporangia described by Renault[887] from the Culm of Esnost are referred to _Hymenophyllites_ on account of the position of the annulus, which appears to encircle about two-thirds of the circumference; it is, however, not certain that the annulus is horizontal as in the recent genus.

The Culm species _Rhodea patentissima_ described by Ettingshausen[888] as _Hymenophyllites patentissima_ and subsequently referred by Stur[889] to _Rhodea_, is regarded by these authors as closely allied to _Hymenophyllum_ simply on the ground of the finely divided and delicate sterile fronds; another species, _Rhodea moravica_ (Ett.), which Ettingshausen referred to _Trichomanes_, is compared with recent species of that genus. In neither case do we know anything of sporangial characters.

A, E. _Senftenbergia elegans._
B. _Oligocarpia Brongniartii._
C. _Trichomanes_ sp.
D. _Hymenophyllum tunbrigense._
F, G. _Sphenopteris_ (_Hymenophyllites_) _quadridactylites._

(A, B, F, G, after Zeiller; D, after Hooker; E, after Stur.)]

A fertile sphenopteroid frond figured by Schimper as _Hymenophyllum Weissi_[890] from the Coal-Measures of Saarbrücken bears some resemblance to recent Hymenophyllaceae, but the figures are by no means convincing: an examination of the type-specimens in the Strassburg Museum led Solms-Laubach[891] to express dissent from Schimper’s determination. A more satisfactory example is that afforded by the fertile pieces of a frond described by Zeiller[892] from French Coal-Measures as _Hymenophyllites quadridactylites_ (Gutbier). Some of the ultimate segments with a truncated tip are preserved in close association with a group of oval sporangia with a complete transverse annulus (fig. 270, F, G). The position of the sporangia is such as to suggest their separation from a terminal columnar receptacle like that in _Trichomanes_ and _Hymenophyllum_. In his account of this species from the Coal-Measures of the Forest of Wyre, Kidston[893] states that Zeiller informed him that he had noticed traces of what appeared to be a columnar receptacle in the French specimens.

The records of Hymenophyllaceae from the Mesozoic and Tertiary formations are not such as need detain us. The facts bearing on the geological history of this family are singularly meagre. There is no evidence which can be adduced in favour of regarding the Hymenophyllaceae as ferns of great antiquity, which played a prominent part in the floras of the past.

It is interesting to find that the genus _Ankyropteris_[894], one of the Botryopterideae (a group of Palaeozoic Ferns for which I propose the name Coenopterideae), has a morphological character in common with _Trichomanes_, namely the production of axillary buds: there are also features in the stelar anatomy shared by the Botryopterideae and Hymenophyllaceae[895]. These resemblances, though by no means amounting to proof of near relationship, point to a remote ancestry for certain features retained by existing members of the Hymenophyllaceae.

=Cyatheaceae.=