Neuropteridium.

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

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

Fig. 348. Neuropteridium validum, Feist. Nat. size. From the Karharbári Coal-field, India. From Arber, after Feistmantel.

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

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

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

Neuropteridium intermedium (Schimper). Fig. 349.

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

Fig. 349. Neuropteridium intermedium (Schimp.). (After Blanckenhorn. ¼ nat. size.)

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

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