LYMAN: STUDIES OF HYMENOMYCETES. 
143 
gated, but it seems probable that the sporophores are degenerate 
basidia. 
According to Fuckel (’73), Polyporus ( Poria ) metamorpliosus at 
first produces only yellow conidia of the type of Sporotrichum or 
Botrytis. Unfortunately no figures accompany the brief description. 
The most important and interesting conidial form thus far reported 
among the Basidiomycetes is that which Brefeld (’89) discovered in 
his cultivation of Polyporus annosus. In cultures of basidiospores, 
after six to eight days the mycelium produces club-shaped conidio- 
phores of the Oedocephalum type which bear numerous spores exactly 
similar to the basidiospores. These conidia germinate readily and 
produce typical mycelia. The conidiophores show considerable 
variation in form and size, and, when the number of spores is reduced 
to four, they are externally indistinguishable from isolated basidia. 
On account of these conidia, Brefeld removed this species from the 
genus Polyporus and placed it in the new genus Heterobasidion. 
He regards the conidiophore as the original form of the basidium, 
and believes that in this species as in Pilacre and Tomentella, there 
is still preserved the ancestral hyphomycetous form from which the 
Basidiomycete has been derived. 
Summary. 
It will be seen from the above statement that polymorphism appears 
to be very general among the Protobasidiomycetes, the secondary 
spores taking the form of very simple conidia or bud cells; typical 
oidia and chlamydospores have not thus far been found. Confining 
our attention to the Hymenomycetes, and excluding the Dacryomy- 
cetaceae and the Exobasidiaceae from the discussion on account of 
their resemblance to the Protobasidiomycetes, we may review the 
known occurrence of the four types of secondary spores as follows: — 
(а) Bud-cell formation occurs only in isolated cases where the 
spores have apparently germinated under unfavorable conditions. 
(б) Oidia are extremely common in the Agaricaceae, occasional in 
the Polyporaceae, Hydnaceae, and Clavariaceae, and unknown in the 
other families. They are found on the mycelium, never forming a 
fructification of their own, although in certain species of agarics they 
occur in rather definite tufts or clusters. 
(c) Chlamydospores are known in Hemigaster, in a few agarics 
