Fig. 212. Bothrodendron.

In habit a plant of Bothrodendron recalls Lepidodendron and recent species of Lycopodium; the slender dichotomously branched twigs bearing numerous leaves ([fig. 212], D), have been mistaken for shoots of Lycopodium, and fragments of branches might well be identified as impressions of Mosses. The leaf-scars on the smaller shoots occur on elongated cushions ([fig. 212], C, D) with a transversely wrinkled surface; on the older branches the leaf-scars are separated by fairly large areas of bark characterised by sinuous transverse grooves and narrow ridges bearing numerous small pits, as shown on an enlarged scale in [fig. 212], A. The original surface-features are shown on the left of the drawing, and a slightly deeper level in the cortex is represented on the right-hand side. The absence of leaf-cushions on the older shoots is probably the result of secondary thickening, which also alters the size and shape of the leaf-scars. Each scar has three pits on its surface, as in Lepidodendron; a central leaf-trace scar and lateral parichnos scars. The circular pit above the leaf-scars, which occurs in most species, marks the position of the ligule. The relation of the short leaves, 5 mm. long, to the leaf-cushions is shown in [fig. 212], D. The absence of leaves, except in impressions of slender twigs, may be interpreted as an indication that they were shed at an early stage and did not persist many years. The leaf-cushions of the smaller shoots of Bothrodendron minutifolium closely resemble those figured by Weiss on a Devonian plant, Lepidodendron Losseni[616].

One of the few examples so far discovered of a Bothrodendron cone is shown in [fig. 213]; this specimen, at least 10 cm. long, was found by Mr Hemingway in the Middle Coal-Measures of Yorkshire and described by Dr Kidston. Numerous sporophylls are attached at right angles to the axis, the surface of which is protected by their upturned distal portions; the arrangement of the parts appears to be the same as in Lepidostrobus. A specimen figured by Zeiller as Lepidostrobus Olryi, which Kidston is probably correct in identifying with Bothrodendron minutifolium, shows that each sporophyll carries a horizontally elongated sporangium ([fig. 212], E).

b. Bothrodendron punctatum Lindley and Hutton[617]. Figs. [211], [212] B, F.

This species, which is less abundant than B. minutifolium, in British Coal-Measures, has been described by several authors as Ulodendron on account of the occurrence of large depressions, like those shown in [fig. 211], on certain branches of the plant. At the suggestion of Dr Kidston, Prof. Zeiller[618] figured an English specimen of this species, presented to the Paris Museum by Mr Hutton, in which the leaf-scars are preserved on the bark of a stem with Ulodendron scars. The surface of the bark is characterised by numerous small pits and discontinuous vertical lines in contrast to the transverse lines of B. minutifolium (cf. [fig. 212], A and F). The leaf-scars on the smaller shoots may have a diameter of only 0·3–0·5 mm., while on the larger branches they reach a breadth of 1 mm. The ligule-pit may be in contact with the upper edge ([fig. 212], F) of the leaf-scar or separated from it by a short distance.

Fig. 213. Bothrodendron minutifolium Cone. From a specimen in Dr Kidston’s Collection. (Slightly reduced. Kidston (02) Pl. LIX.)