[Vor. 3 
204 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
Hypochnus is separated from Thelephora, as I have limited 
the latter, by strictly resupinate habit; from Corticium and 
Pemophora by rough-walled to echinulate spores which are 
usually, but not always, distinetly colored; from Zygodesmus 
of the Hyphomycetes by true basidia which bear two or more 
spores; and from Grandinia and Odontia of the Hydnaceae 
by loosely interwoven, hypochnoid structure and more or 
less colored, rough-walled to echinulate spores. 
As here treated, the species of Hypochnus form a natural, 
compact group at the foot of Hymenomycetes, with simple 
basidia, and closely resembling Zygodesmus in general habit 
and also in form and color of spores. Hypochnus is so 
closely related to Thelephora and Grandinia that many of 
its species have been published in those genera, as will 
be seen by the synonymy of species, or occur in those genera 
under manuseript names in the large herbaria. 
The species of Hypochnus are apparently humus formers, 
for the fructifications are found under very rotten wood and 
other organie matter rather than on nearly sound wood. 
Hence they probably follow other fungi in wood destruc- 
tion. 
This is the first presentation of the North American species 
of Hypochnus. It shows the geographical distribution of 
the genus localized in the northeastern United States and 
along our Atlantie coast and ranging westward aeross the 
northern United States. Not an Hypochnus has been found 
in a series of 175 numbers of Thelephoraceae, mostly re- 
supinate, collected by Dr. and Mrs. Murrill in Mexico. 
The sketches of microscopic details of the species in this 
part were made by the aid of a camera lucida from prepara- 
tions of such type or authentic specimens as are referred to 
in the accompanying text. 
The development of the present conception of Hypochnus 
is of historical interest. When first published, Hypochnus 
comprised species which I refer to Hypochnus and Corticium; 
then tropical lichens predominated; in his last work Fries 
excluded the lichens, recognized the close relationship to 
Corticium and placed both Coniophora and Hypochnus as 
