40 ASCOM YCE TES 



2. Ascocarps subterranean, mostly enlarged, tuberous. 3. 

 Ascocarps not subterranean, mostly small. 4. 



3. Peridium clearly distinct from the walls of the ascocarp ; spore masses 



powdeiy at maturity. Elaphomycetaceae. 



Peridium not clearly limited, continuous with the walls of the ascocarp ; 



spore masses never powdery. Terfeziaceae. 



4. Ascocarps mostly sessile ; peridia usually remaining closed. 



Aspergillaceae. 



Ascocarps mostly stalked ; peridia opening at maturity by lobes or 



irregularly. Onygenaceae. 



Ascocarps sessile, the spore masses exuding in columnar masses from 



'the goblet-shaped peridia. Trichocomaceae. 



Of the above families, the Elaphomycetaceae, Onygenaceae 

 and Trichocomaceae are each made up of a single genus from 

 which the respective families receive their names. The subter- 

 ranean Terfeziaceae are made up of eight genera, while the mould- 

 like Gymnoascaceae and Aspergillaceae are more numerous, the 

 former with live and the latter with fourteen genera. 



LITERATURE. 



Saccardo. Sylloge Fungorum, 1 : 60-71 ; 8 : 863-872 ; 9 : 413- 

 431 ; II : 441. 



Fischer. Die natiirlichen Pflanzenfamilien, ii: 290-320. 



Ellis & Everhart. North American Pyrenomycetes, 45-49. 

 1892. 



Martin. Synopsis of the North American Species of Asterina, 

 Dimerosporium and Meliola. Jour. Myc. i : 133-139, 145-148. 

 1885. 



Order 5. PERISPORIALES. 



The Perisporiales form a small group of partly parasitic and 

 partly saprophytic fungi some of w^hich form a simple and easily 

 studied group, as they are abundant and widely distributed. To 

 illustrate the general characters of this group we can do no better 

 than to describe the structure of the powdery mildews. These 

 are the most typical examples of external parasites and take their 

 popular name from the white powdery conidia that are produced 

 early in the season. The parasite forms masses of cobwebby 

 mycelium on the surfaces of various leaves. A common ex- 



