MISCELLANEOUS CROPS. 



157 



The larvsB of this moth (already described) feed on the 

 roots of lettuces. 



The Lettuce Mildew {Peronospora ganglioniformis, 

 Fig. 51) produces pallid patches on lettuce leaves, and " in 

 bad cases summer lettuces are quickly reduced to pu- 

 trescent masses." The conidiophores of this fungus are 



Fig. 51. — Lettuce Mildew [Peronospora ganglioniformis). 



A. A conidiophore and conidia. 



B. Oospores (reeting-spores). 



X 195 diam. (Zeiss's C. and 3 CO.). 



flattened and slightly twisted (Fig. 51 A). Each terminal 

 branch has a cup-like expansion bearing on minute 

 spicules from three to five conidia. The conidia germinate 

 upon the leaves and give rise to mycelia within and upon 

 the host-plant. Like Peronospora parasitica and other 

 species of the Peronosporece, the lettuce mildew produces 

 oospores (Pig. 51 B) which hibernate " in the old rotting 



