Neuropteris.
The fronds for which Brongniart[1528] created this genus, though suspected by Stur in 1883 as wrongly classed among the ferns, have only recently been shown to be the leaves of Pteridosperms. As yet only one case is recorded in which
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).
Fig. 371. Neuropteris heterophylla. From a specimen in the Manchester Museum. ½ nat. size. M.S.
As shown in [fig. 371] which represents a primary pinna, the small pinnules on the lower branches are gradually replaced in the upper portion of the specimen by falcate segments.
Neuropteris macrophylla, Brongniart[1539]. Figs. [354], D, D′; [372].
The rachis of the large fronds of this species illustrates the dichotomous habit of many Neuropteris fronds, also the occurrence on the petiole of large Cyclopteroid pinnules (cf. [fig. 370]). The small piece of a pinna reproduced in [fig. 372] shows the slender attachment of the segments, the blunt apex, and the Neuropteroid venation. Single pinnules of this species may be distinguished from those of N. Scheuchzeri by the blunter apex, the absence of the pair of small Cyclopteroid pinnules on the same branch and by the absence of hairs. N. macrophylla is characteristic of the Upper Coal-Measures of Britain.
Fig. 372. Neuropteris macrophylla, Brongn. From a photograph by Mr Hemingway.
Neuropteris Scheuchzeri, Hoffmann. Figs. [354], F; [373].
Fragments of this well-known Coal-Measure species were figured by Scheuchzer in his Herbarium Diluvianum[1540] as Lithosmunda minor, and by Lhywd (Luidius[1541]) as Phyllites mineralis as early as 1760. Neuropteris Scheuchzeri, so named by Hoffmann in 1826, is a type which many authors have described under different names. Lesquereux[1542] figured it as N. hirsuta from the Coal-fields of Pennsylvania, and under the same name it is recorded by Fontaine and White[1543] from Permian rocks of Virginia. The oval patches on the surface of a pinnule described by these authors as sori are certainly not of that nature. The same species is described by Bunbury[1544] from Nova Scotia as N. cordata Brongn. var. angustifolia. For a full synonymy of the species reference should be made to lists published by Kidston[1545], White[1546], and Zeiller[1547].
Fig. 373. Neuropteris Scheuchzeri. From a specimen (v. 2009) in the British Museum. ¾ nat. size.
The large tripinnate fronds are characterised by the long linear- or oval-lanceolate pinnules ([fig. 373])[1548] with a pointed apex and numerous bristle-like hairs on the lamina; two much smaller Cyclopteroid segments occur at the base of the pinnae which are terminated by the linear leaflets ([fig. 354], F, p. 535).
Neuropteris Scheuchzeri is characteristic of the Upper and Middle Coal-Measures of Britain and is recorded from several localities in North America and the Continent. Zalessky[1549] has recently recorded the species from the Coal-Measures of Donetz. The frequent occurrence of detached pinnules points to a caducous habit. Even single leaflets can, however, be identified by their large size, the pointed apex, and hairy lamina. The hairs are preserved as fine oblique lines simulating veins; they were so described by Roemer[1550] who took them for cross-connexions between the secondary veins and referred the pinnules to Gutbier’s genus Dictyopteris.
Another example of Neuropteris with hairy pinnules is described from the Commentry Coal-field by Renault and Zeiller as N. horrida[1551]. The oval-linear, bluntly rounded, pinnules are characterised by a median band of hairs on each surface and a narrower strip at the edge of the lamina.