Fes, 198. ] LEPIDODENDRON VELTHEIMIANUM. 331 
have been met with in actual tissue connection with stems. 
Professor Williamson referred these strobili to the Lepido- 
dendron common in the same blocks (viz, Lepidodendron 
Veltheimianum) on the ground of their association 
(Williamson, 1872). Messrs. Kidston and Binnie, after 
research on megaspores occurring in the Carboniferous 
strata, have come to the same conelusion. The probabilities 
are, then, that these strobili were the fructifications of 
Lepidodendron Veltheimianum, and as this prothallus is in 
a megaspore identical with those occurring in the hetero- 
sporous strobili mentioned above, I have referred it to that 
species. The strobili bear microsporangia in the apical 
part and megasporangia towards the base. The megaspores 
have a thick reddish-brown coat covered by knobbed spines, 
while three ear-like lobes of the spore wall can be seen at 
the apex of the spore. In the specimen figured there are 
two of the processes referred to, and at these two places 
the wall shows a certain amount of splitting, so that the 
protuberances are at least partly due to rupturing of the 
spore coat to expose the archegonia Most of these mega- 
spores (which occur in great abundance throughout the 
blocks) have no tissue inside them, and, when we consider how 
delicate prothalloid tissue is, this is not surprising. Some- 
times, however, they are filled with scattered or broken-up 
cells, and occasionally with a continuous cellular tissue. In 
the last case it is justifiable to consider it as a prothallus. 
In the specimen figured the plane of section is almost 
radial longitudinal. It passes through the area enclosed by 
the three lobes, and which is presumabiy the apex of the 
megaspore, and there we should expect to see archegonia if 
they were present. While I cannot definitely say this is the 
case, there is at least a cap of small-celled tissue comparable 
with the archegonial tissue of Selaginella. Probably the 
specimen was not quite mature, for there is no distinct gap 
in the spore wall at the ear-like lobes, and this immaturity 
may explain the absence of archegonia. The rest of the 
prothalloid tissue is of larger-celled parenchyma, the line of 
demarcation being quite distinct though not constituting 
a diaphragm. This small-celled archegonial tissue at the 
apex of a larger-celled prothallus is essentially similar in 
Selaginella, while the splitting of the spore coat along three 
