Chapter XXXIII: Cordaitales (3)

The generic name _Niponophyllum_[747] was proposed for some petrified specimens of leaves or possibly leaflets from Upper Cretaceous beds in Japan which, though not definitely assigned to a group or family, are considered by the authors of the genus ‘to lie [anatomically] somewhere between _Cordaites_ and _Cycadeoidea_’ ‘with a closer similarity to the former than to the latter if we compare the whole _Cordaites_ leaf with our blade.’ The data on which this conclusion is based are, however, insufficient to justify a reference of _Niponophyllum_ to the Cordaitales or indeed to lend any substantial support to the opinion that the Japanese specimens are anatomically more akin to _Cordaites_ than to other plants. The type-species is represented by two specimens of leaf-fragments about 0·4 mm. thick and from 6 to 9 mm. broad containing from 21 to 33 vascular bundles; the upper part of the mesophyll is composed of palisade tissue and the stomata appear to be confined to the lower epidermis. Each bundle is accompanied by an =I=-shaped girder, and small patches of sclerenchyma occur next the upper epidermis between the girders; there are no resin-canals: the vascular bundles are collateral, the xylem is said to be almost entirely centripetal and exarch, but in the absence of evidence afforded by longitudinal sections the details of structure cannot be definitely determined. A comparison is made with Cycadean leaves and with leaves of Araucarineae and Podocarpeae, also with _Cordaites_; another type with which _Niponophyllum_ may be compared is _Desmiophyllum Solmsi_[748].

The genus is interesting as an example of a petrified gymnospermous type of leaf characterised by the absence of resin-ducts and transfusion-tracheids, the possession of collateral, apparently exarch, bundles enclosed in a double sheath; but the data supplied are insufficient to enable us to allocate the specimens to a position within the class.

A specimen described by Schenk[749] as _Eolirion primigenium_ from Lower Cretaceous beds in the Carpathian mountains closely resembles in habit a foliage-shoot of _Poa-Cordaites_; the leaves are narrow and linear with obtuse apices and attached, apparently, in a close spiral. Schenk assigns the plant to the Monocotyledons, but its systematic position must be left unsettled.

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The list of Mesozoic specimens resembling _Cordaites_ leaves might be extended. Apart from some Triassic and Rhaetic examples which may well be Cordaitalean, there are many others which, though similar in form and venation to _Cordaites_, are in all probability more closely related to _Agathis_ and other genera; the species _Dammarites Bayeri_ recently described by Zeiller[750] from the Upper Cretaceous of Bulgaria is a case in point. The Araucarian character of the wood of _Cordaites_ precludes any satisfactory discrimination between Mesozoic Araucarian stems and those of Cordaitalean species, at least in the case of such material as is usually available.

=Titanophyllum.= Renault.

_Titanophyllum Grand’Euryi_ Renault. The remarkable leaves on which this genus and species are founded[751] were discovered in the Commentry coalfield; they occur as detached specimens and cannot be correlated with any known stem. Renault suggests that the Autun stems referred to _Colpoxylon_ may have borne the _Titanophyllum_ leaves, but this correlation rests only on the dimensions of the stems and the occurrence of transversely elongated scars on the surface. The lamina is thick and coriaceous, 70–75 cm. long and 20–25 cm. in breadth; the veins are parallel but not branched; numerous longitudinal striations on the upper surface indicate the presence of hypodermal stereome-strands; stomata are abundant on the lower surface and the more or less rectangular cells in the neighbourhood of the stomata appear to be papillose (fig. 485, A, B). The distal region of the lamina is often torn into strips (fig. 485, A); the approximately rectangular leaf has a broad elliptical base 9–10 × 3–4 cm.

Dr White[752] describes a specimen from the Lower Coal Measures of Missouri as ? _Titanophyllum Brittsii_ which he speaks of as the thick base of a leaf similar to that described by Renault but, as White says, no formal diagnosis is possible without more satisfactory material. Such evidence as is available suggests that _Titanophyllum_ is a type of Cordaitalean leaf probably closely allied to _Cordaites_.