THE FUNGI WHICH CAUSE PLANT DISEASE 



661 



Soon the sclerotia form as mustard-seed-like bodies. They are 

 produced in great abundance on all media but neither these struc- 

 tures nor the mycelium have yet been seen to bear spores of any 

 kind. The fungus was first studied by Halsted =' and later by 

 many others. It was described and named by Saccardo from speci- 

 mens communicated by Stevens. 



S. cepivorum Berk. 



Minute, spherical, gregarious, black. It is found on various 

 species of Allium, causing rot. 



Fig. 447. — S. roUsii, sclerotia. After Halsted. 



S. rhizoides Auer.^-^ 



Subglobose, at first white-villose, then smooth, black, rugose. 



On Calamagrostis and other grasses. It causes considerable 

 injury to the ha}' crop in Europe. 



S. tuUparum Klebahn,"*-' S. tulipae Lib. and S. bulborum Wak. 

 are found on tulips, -and other bulbs. A relation to Sclerotinia is 

 usually assumed but has not been demonstrated. See p. 136. 



S. oryzae Catt. is found on rice in Japan and Italy. 



Ozonium Link. (p. 659) 



Cobwebby or byssoid, cespitose, hyphse densely interwoven, 

 primary hyphse fasciculate. 

 Some twelve species. 



