THE FUNGI WHICH CAUSE PLANT DISEASE 73 



The most important species are C. tenue Nowak. on Acorus 

 and Iris; C. graminis Biisg." on various grasses, C. violae Berlese 

 on violets. ^^ 



C. viticulum Pru.^ and C. mori Pru.^* have been described on 

 grape and mulberry, but further study is very desirable. 



C. brassicse E. & B.^^ is described from dead leaves of cab- 

 bage. 



C. caespitis G. & M.^® occurs in France on Lolium. 



Pyroctonium sphaericum Pru.^^ was reported in 1894 as the 

 cause of wheat disease in France but has not since been 

 found. 



Oochytriaceae (p. 67) 



The plant body is either an undifferentiated cell or a well de- 

 veloped mycelium; reproduction by means of asexual swarm 

 spores and sexual resting spores. Of the three genera only one 

 is of economic importance. 



Key to Genera of Oochytriaces 



Mycelium entirely lacking 1. Diplophysa. 



Mycelium present 



Mycelium producing a single gametan- 



gium 2. Polyphagus. 



Mycelium producing several gametangia 3. Urophlyctis, p. 73. 



Urophlyctis Schroter 



Mycelium endophytic, producing zoosporangia on the surface 

 of the host and thick- walled oospores within the tissues; zoospores 

 uniciliate. The genus contains some half dozen species all of 

 which are parasitic on higher plants. 



U. leperoides (Sacc. & Trab.) Magnus^*'" causes "beet root 

 tumor," in North Africa and Western Europe. The rootlets of 

 .the upper portion of the root are attacked and develop tumorous 

 growths, sometimes as large as a walnut. The infection is super- 



