KIDSTON : THE FLORA OF THE CARBONIFEROUS PERIOD. 345 
size of the stem, the two lateral rows of leaves are large, single-nerved, 
and sickle-shaped, while the two ventral rows are very small and 
closely adpressed to the stem. Such types have a great resemblance 
to some forms of Selaginella. In other species the leaves appear to 
be whorled as in Lycopodites Stockii Kidston. 
In some cases the fructification is in the form of terminal cones. 
The sporangium is placed at the base of the bract, and in form and 
position, as far as one can observe from impressions, seems to agree 
entirely with that of Lycopodium. In the other case the sporangia 
are borne at the base of the leaves on an ordinary branch, which has 
apparently undergone little or no modification, as in Lycopodites 
ciliatus Kidston. Such forms compare with the common Lyco- 
podium selago of our hills and moors. 
It is not yet known whether Lycopodites produced only one 
kind of spore (isosporous) or two kinds, macrospores and microspores 
{heteros porous). 
Another genus which is placed in this group is ArchceosigiXlaria 
Kidston, represented by a single species, Archceosigillaria vanuxemi 
Gopp., sp. It is very rare, and the only examples I have seen are 
from the Lower Carboniferous of Westmorland. 
II.— LEPIDODENDRE.E. 
Lepidodendron Sternberg. This is one of the most common 
genera of Carboniferous plants, and occurs plentifully throughout 
the whole formation. 
The Lepidodendra were of arborescent dimensions, attaining 
a height of a hundred feet, with trunks two feet and over in diameter. 
The stem divided dichotomously and formed a much ramified head 
(Plate LYL, fig. 1). The outer surface of the bark bears contiguous 
(Lepidodendron aculeatum Sternberg, Plate LL, fig. 1), or more or 
less distant (Lepidodendron serpentigerum Konig sp., Plate LL, fig. 2) 
rhomboidal or fusiform leaf -cushions, on whose surface, generally 
above the centre, is situated the leaf -scar. Within the leaf-scar are 
three punctiform cicatricules, the central being the vascular scar; 
