90 



THE FUNGI WHICH CAUSE PLANT DISEASE 



S.graminicola (Sacc.) Schr.,^''' °' infects leaves and inflorescences, 

 the oospores causing marked distortion of the latter and rapid 

 disintegration of the former; conidiophores 100 x 10-12 n, conidia 

 20 X 15-18 im; oogonium wall thick, 4-12 fi, at maturitj' 30-60 fi 

 in diameter, reddish-brown; oospore pale-brown, 26-36 /i. 



The conidial phase is not prominent, while the oospores by their 

 disintegrating effect upon the leaves of the host, render the plants 

 quite conspicuous and closely simulate the habit of a brown smut. 



Fig. 61. — S. graminicola. 

 Conidiophores and co- 

 n i d i a ; germinating 

 conidia and zoo- 

 spores. After Butler. 



Fig. 62. — S. graminicola, oo- 

 gonium, oospore and an- 

 theridium in section. Af- 

 ter Stevens. 



On millet (Setaria italica), pearl millet, fox tail and com; in India 

 of considerable economic importance.^* 



S. macrospora Sacc. has been reported in com tassels and on 

 wheat in Italy and the United States.*^' ^ Conidia unknown; 

 oogonia embedded firmly in the tissue of the host, not causing 

 disintegration as in S. graminicola; oospores Ught yellow, smooth, 

 60-65 M- 



Plasmopara. Schroter (p. 83) "* 



The tree-like, branching conidiophores. Fig. 63, are common to 

 this genus, Peronospora, Peronoplasmopara and Bremia, and 

 unlike the conidiophores of Phytophthora they are completely 

 formed before they begin to bear spores. 



Mycehum branched; haustoria simple; conidiophores erect. 



