174 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
but their formation soon spreads to the clamped hyphae, and the spore 
production in a short time becomes as copious as on the clampless 
mycelia. 
This variation in the character of the young mycelia is not dependent 
on differences in the culture media or on other conditions of environ¬ 
ment, since the two types of mycelia may arise from neighboring 
spores in the same drop culture, or both types of hyphae may arise 
together,— a germ tube with clamps appearing at one end of the spore, 
and one without clamps at the other end (pi. 20, fig. 61). Thus it is 
seen that primary and secondary mycelia, which are so clearly defined 
in Corticium alutaceum, are not sharply differentiated in this species. 
It is possible, however, that cytological study may reveal some funda¬ 
mental distinction. 
Reproduction in cultures .— In drop cultures the growth of the 
mycelium is very limited, being soon checked by the copious produc¬ 
tion of conidia on which the entire vitality of the culture is expended. 
In agar tubes, also, the mycelium does not form an extensive growth 
on most media. Prune decoction seems especially suited to vegeta¬ 
tive development, and here, in addition to the usual abundant forma¬ 
tion of conidia, an imperfect basidiosporic hymenium is frequently 
produced at the upper end of the tube. In wood cultures there is a 
sparse development of superficial mycelium followed after about two 
months by a fairly extensive development of basidiosporic hymenium. 
This hymenium agrees in every way with that collected in the field. 
No oidia or chlamydospores were observed in any culture. 
Conidia .— Conidia are produced on all mycelia, appearing on the 
fourth or fifth day in the case of mycelia without clamps and one or 
two days later on clamped mycelia. The formation is abundant in all 
media, even a very attenuated decoction producing them liberally, 
while in drop cultures in which a medium of fair concentration is used, 
the formation is so copious that the vegetative growth of the mycelium 
is checked and the surface of the hanging drop becomes clouded by the 
mass of discharged spores. 
The conidia are hyaline, thin-walled, allantoid, and agree with the 
basidiospores in every particular save that they more frequently con¬ 
tain refractive guttulae and are longer, being 2-2.7 p in diameter by 
6-9 p in length (pi. 20, fig. 70). They occur in groups of from two to 
ten borne on low elevations on the sides of the hyphae (pi. 20, fig. 69). 
These groups are at first scattered here and there over the mycelium. 
