PIRICULARIA. 



Piricularia. 



503 



Oonidia grey, pluricellular, somewhat pear-shaped, and pro- 

 duced from the apex of simple erect conidiophores. 



Piricularia oryzae Br. et Cav. This species is described 

 by Briosi and Cavara as causing a disease of rice in Northern 

 Italy. The plants become spotted and reddish-brown in summer, 

 finally withering. The conidiophores arise on the spots on the 

 lower surface of the leaf, and bear light-grey three-celled 



Fio. 308. — Mojtigosporium album, (v. Tubeuf deL) 



oonidia. Diseased plants may be found bearing this fungus 

 only, frequently however it is in company with other fungi. 



Cercosporella. 



Conidia hyaline, similar to those of Cercospora, and produced 

 from simple or branched hyaline conidiophores. 



Cercosporella persica Sacc. is parasitic on living leaves of 

 peach. In America it has been known since 1890, and receives 

 the name of "frosty mildew." It causes yellow spots on the 

 lower surface of the leaf. 



0. pastinacae Karst. occurs on living leaves of cultivated 

 parsnip. 



