[Vol. 3 

 204 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



Hypochrms is separated from Thelephora, as I have limited 

 the latter, by strictly resupinate habit ; from Corticium and 

 Peniophora by rough-walled to echinulate spores which are 

 usually, but not always, distinctly 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 ThelepJiora 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 manuscript names in the large herbaria. 



The species of Hypochnus are apparently humus formers, 

 for the fructifications are found under very rotten wood and 

 other organic 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 Atlantic coast and ranging westward across 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 

 Cortici/wm and placed both Coniophora and Hypochnus as 



