Neuropteris pinnae occur in organic connexion with seeds[1529], but it is almost certain that the genus as a whole must be placed in this generalised group. Renault[1530] pointed out that the petioles of Neuropteris fronds from Autun had the anatomical features of Myeloxylon (petiole of Medullosa). Since Kidston’s important discovery of seed-bearing pinnae of N. heterophylla, Grand’Eury[1531] has recorded the association of Neuropteris fronds with seeds in French Coal-fields. By some of the older authors Neuropteris was compared with Osmunda because of a similarity in venation. In the frequent dichotomy of the frond and in the occurrence of pinnules on the rachis, Neuropteris closely resembles Odontopteris[1532]: there can be little doubt as to the close relationship of the Pteridosperms possessing these two types of foliage. Neuropteris may be defined as follows:
Fronds reaching a considerable size, probably in soma cases a length of 10 metres[1533]; bi- or tri-pinnate; the rachis may be dichotomously branched (figs. [354], D; [370]); both rachis and petiole bear single pinnules, those on the latter frequently differ from the normal leaflets in their larger Cyclopteroid laminae ([fig. 370]). Pinnules entire, rarely slightly lobed, broadly linear, attached by a small portion of the base, which is usually more or less cordate. In N. Grangeri Brongn. the pinnules are attached by a short pedicel[1534]. The midrib always dies out before reaching the blunt or pointed apex of the lamina and gives off at an acute angle numerous secondary veins characterised by their arched course and repeated forking.
Fig. 370. Neuropteris frond with Cyclopteris leaflets. English Coal-Measures. (From a block given to me by Mr Carruthers. A.C.S.)
Potonié describes the secondary veins of the pinnules of Neuropteris pseudogigantea[1535] as occasionally anastomosing, a feature which may be regarded as a step towards the reticulate venation of the closely allied genus Linopteris.
Renault[1536] described some petrified pinnules of Neuropteris in which the mesophyll shows a differentiation into upper palisade tissue and lacunar tissue below; the lower epidermis is infolded at intervals where grooves (probably stomatal) occur like those on the leaves of an Oleander (Nerium oleander).
The rachises of Neuropteris fronds are described by Grand’Eury under the generic name Aulacopteris[1537].
Neuropteris heterophylla, Brongniart[1538]. Figs. [354], E; [371].
This species is characteristic of the Lower Coal-Measures of Britain; it occurs also in the Middle Coal-Measures and is a common type in Upper Carboniferous rocks in various parts of the world. The fronds are large and tripinnate, the rachis is often dichotomously branched and Cyclopteroid pinnules may occur on the petiole. The pinnules, 5–20 mm. in length and 3–8 mm. broad, have a rounded apex ([fig. 354], E, p. 535).
