LYMAN: STUDIES OF HYMENOMYCETES. 
193 
like that of Lentodium, but belongs to the type seen in Cortinarius. 
Moreover, the hymenial region is composed of gills which, although 
anastomosing to some extent near the stipe, do not form closed cham¬ 
bers. Hence this genus, even though it be accepted on the scant evi¬ 
dence of but two specimens, cannot be accounted a near relative of 
Lentodium and the latter genus must, for the present, remain isolated. 
General Considerations. 
Tlie vegetative mycelium. — In the greater number of species culti¬ 
vated two periods are clearly discernible in the development of the 
mycelium; these are designated in this paper as primary and second¬ 
ary mycelia. The primary mycelium is the product of the germina¬ 
tion of the basidiospore and is distinguished by absence of clamps, and 
occasionally, as in Corticium alutaceum, by smaller diameter of the 
hyphae. The hyphae of the primary mycelium soon lose their pro¬ 
toplasm and disappear. The secondary mycelium arises from the 
primary in from one to eight days as the direct continuation of the 
growth of the latter; it is composed of hyphae of normal size and in 
the great majority of species produces numerous clamps. In certain 
species no primary mycelium can be distinguished for the basidiospore 
gives rise at once to a clamped hypha of normal size. In such cases 
there is either no primary mycelium or its presence cannot be detected 
by the customary signs. In Corticium roseo-pallens the habit of ger¬ 
mination is not uniform, for some basidiospores produce clamped, 
and others clampless germ tubes. Again, in species like Corticium 
subgiganteum which has no clamps at any time, no division into pri¬ 
mary and secondary mycelia is possible by either criterion mentioned 
above. 
Both primary and secondary mycelia produce chlamydospores in 
equal profusion, but on germination these spores invariably give out 
clamped germ tubes. In the formation of oidia, both types of mycelia 
are equally active, although the oidia are not usually formed directly 
from the clamped hypha, but from smaller branches of the size and 
appearance of the primary hyphae. On germination, oidia form un¬ 
damped germ tubes. Conidia also occur on both types of mycelia, 
and where they are of a highly differentiated nature they agree with 
the basidiospores in the character of the mycelia produced on germi¬ 
nation; thus the conidia of Corticium roseo-pallens sometimes give 
