1897] NOTES ON THE GENUS CALOSTOMA 185 
occurring on a single basidium varies from five to ten or twelve. 
My material contained no specimens with the mature spores still 
in situ; but in that which I examined, although the spores were 
considerably advanced, there were no sterigmata. 
In his monograph, already referred to, Massee describes and 
figures the basidia as ‘broadly obovate, measuring from 40~50 
* 15-20n, and bearing five or sometimes six spores supported 
on minute wart-like prominences arranged in a circle around the 
apex.” In my material, however, the position of the spores is 
very characteristic, and in no specimen which I] examined were 
they in the least confined to the apex of the basidia, nor did 
they show any tendency to a circular arrangement in this 
region. 
The fact that the spores are borne laterally upon the basidia 
in Calostoma seems to point at once to its affinity with Tulo- 
stoma, the only other gastromycete in which the spores are simi- 
larly borne. Fischer is of the opinion that the double peridium 
in Calostoma indicates its affinity with Geaster; a view also 
Supported by Massee. The latter observer homologizes the 
external peridium of Geaster with the exoperidium and endo- 
peridium of Calostoma, and the inner peridium of Geaster with 
the spore sac in Calostoma. He calls attention, however, to the 
wide difference which exists in the fact that in Geaster the inner 
peridium is confluent with the base of the outer peridium, while 
in Calostoma what he considers as the morphological equivalents 
of these two elements are confluent at the apex. The affinity of 
Calostoma with Tulostoma, however, seems to offer a more sim- 
ple explanation of the facts. If we consider that the part of the 
peridium immediately surrounding the gleba in Tulostoma 
_ becomes differentiated to form the spore sac, but still remains 
attached to the outer shell of the peridium (endoperidium) at 
the apex, and that the rest of the peridium becomes” differen- 
tiated into three layers (volva, exoperidium, and endoperid- 
ium), we see how readily the differences between the two genera 
_ may be explained. Both Calostoma and Tulostoma agree in 
a : : = forced to the surface bile the extension ofa footstalk. In 
