LYMAN: STUDIES OF HYMENOMYCETES. 
195 
chlamydospores in an entirely different category from conidia, for the 
former bodies represent the undeveloped primordia of the conidio- 
phores. Also, says Brefeld, the smut spores of Ustilagineae and the 
aecidio-, uredo-, and teleutospores of Uredineae are morphologic¬ 
ally chlamydospores, and the morphological and systematic relations 
of these groups cannot be understood until the nature of these spores 
is understood. The smut spore germinates by the formation of a 
sporophore, but in the Uredineae the teleutospore alone retains this 
power, the uredospore and aecidiospore putting forth germ tubes 
directly, as is the case with the chlamydospores of Hymenomycetes. 
From his culture studies the writer disagrees with Brefeld in think¬ 
ing that the oidium and the chlamydospore as exemplified in the 
Hymenomycetes can be satisfactorily interpreted as morphologically 
. identical. He has tried in vain to duplicate with species of Hymeno¬ 
mycetes the experiment of Brefeld with Mucor racemosus, viz., by 
varying the culture media and the culture conditions to induce the 
formation of oidia in species which naturally produce only chlamydo¬ 
spores, and vice versa. The copiousness of formation was easily 
modified, but in no case were both types of bodies produced on the 
mycelia of one species, under either natural or artificial conditions, 
nor were transitional states between the two seen. 
The two forms differ in many respects, some of which seem quite 
fundamental. Oidia are merely the cells of the vegetative hyphae 
which separate from one another but show no especial differentiation 
of either walls or contents; the retention of vitality is short. On the 
contrary, chlamydospores are encysted cells formed endogenously in 
the parent hypha by the contraction of the protoplasm which then 
becomes surrounded by a resistant endospore in addition to the origi¬ 
nal cell wall. These spores are very retentive of vitality and are freed 
only by the decay of the hypha walls. Moreover, while the two types 
of spores are found on both primary and secondary mycelia alike, 
oidia produce primary mycelia on germination, while chlamydospores 
give rise to secondary mycelia, a fact which may indicate some cyto- 
logical or physiological distinction between them. 
Both kinds of spores appear occasionally to approach the dig¬ 
nity of conidia. Such an advance in the development of oidia is seen 
in Coprinus, Psathyra, and Psilocybe (Brefeld, ’77, pi. 6; ’89, pi. 
3), where the oidia are borne in particular places and form more or 
less specialized tufts or clumps. In Corticium alutaceum the spores 
