138 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
the formation of oidia to the mature fructification, and concluded 
that the oidium form is a definite stage in the life cycle of many of the 
higher fungi. In certain species almost the whole mycelium becomes 
disarticulated to form oidia; in other species only certain hyphae 
produce oidia during a limited period of the growth of the mycelium; 
while in still more specialized cases, the oidia are formed in particular 
places, and more or less differentiated clusters are produced, as in 
species of Psilocybe, Psathyra, Coprinus, etc. In such cases the 
oidia frequently seem to be incapable of germination, and were thought 
by Hoffmann (’56), Reess ('74), Eidam (’75), Van Tieghem (’75a), 
and others to be spermatia or male cells. A little later Van Tieghem 
decided that they had no sexual significance since he had observed 
their germination, and moreover, had seen the development of normal 
basidiosporic fructifications in the entire absence of the supposed 
spermatia. From the experiments of Van Tieghem, Brefeld (’77, 
’89), and others, it seems clear that these alleged spermatia are merely 
oidia of more specialized type which appear to have lost the power of 
germination in many instances. 
Chlamydospores have not been reported in many genera of the 
Agaricaceae. Fayod (’89a) mentions them as occurring in the stipe 
or pileus of a number of species, but Brefeld (’89) found them only 
in Nyctalis. This interesting genus has been studied by many investi¬ 
gators. In the mature fructification of Nyctalis asterophora Fr., 
the whole upper part of the pileus is composed of thick-walled stellate 
chlamydospores which form a yellowish brown layer about one milli¬ 
meter or more in thickness. In smaller specimens, especially, this 
layer of chlamydospores encroaches so far as to hinder the formation 
of basidia and gills below. In Nyctalis parasitica (Bull.) Fr., the 
chlamydospores are found in the subhymenium, the thick swollen 
lamellae of mature specimens being composed almost entirely of 
narrowly ellipsoid, smooth chlamydospores, so that the production 
of basidiospores is nearly or quite suspended. The chlamydospores 
of Nyctalis have given rise to considerable controversy. Tulasne 
(’60) was the principle advocate of the theory that the chlamydospores 
are organs of species of Hypomyces growing parasitically upon certain 
agarics. De Bary (’59), on the contrary, held that the chlamydospores 
are not due to parasitism, but are organs of two natural species of 
Nyctalis, and the truth of this theory is conclusively proven by other 
observers. Krombholz (’31) sowed chlamydospores on the pileus 
