186 BOTANICAL GAZETTE [MARCH 
Calostoma this footstalk is surrounded in its younger stages by 
the volva and exoperidium, and is plainly seen to arise from 
the endoperidium (fig..6). In Tulostoma the footstalk is like- 
wise surrounded in its younger stages by a portion of the perid- 
ium, which we may consider to be equivalent to the volva and 
exoperidium in Calostoma, and the inner region of the peridium 
from which the footstalk arises is probably the morphological 
equivalent of the endoperidium. 
The similarity which exists between the basidia of the two 
genera is very close indeed, the greatest difference being that in 
the species of Calostoma under consideration the number of 
spores on a single basidium is considerably larger. Schrceter’s 
original figure of the basidia of Tulostoma represents the spores 
with scarcely any sterigmata, and in his description he speaks 
of their nearly sessile character, so that the difference which 
exists in this respect is very slight. 
Briefly stated, then, the evidence which seems to point to the 
affinity of Calostoma with Tulostoma rather than with Geaster, 
is found in the fact that both genera possess a form of basid- 
ium found in no other gastromycete, while the basidia of 
Geaster are entirely different ; and that in explaining the differ- 
ences which exist between Calostoma and Tulostoma by a simple 
process of evolution, no such obstacle has to be overcome as is 
found in the fact that, in Calostoma, the spore sac and endoperid- _ 
ium are united at the apex, while in Geaster what Massee con- 
siders their morphological equivalents are united at the base. 
The anomalous character of such a type of basidium in so 
highly developed a gastromycete, which finds its only parallel 
within the group in the four-spored basidia of Tulostoma, is 4 oe 
matter of some interest in connection with any attempt to draw 
comparisons between the typical basidiomycetes and the sup- 
posed transitional forms. In the present instance it must be 
admitted that (assuming the basidial nature of the sporophores: ay 
of Pilacre) the peculiar basidia just described, together with the 
number, position and sessile character = the Ae would Ss 
render c comparatis 
oe easy the re ae Pro- — : 
