16 Bulletin 313 



Peronospora effusa (Grev.) Rab. — On leaves of spinach and 

 other species of Chenopodiacese and on some species of Plantagin- 

 acese. Causes water-soaked spots and finally the death of the dis- 

 eased parts. Yellowish or brownish discolorations on the under side 

 of the leaf. Conidiophores violet-tinted in mass, 150-400 x 7-9 /x, 

 branched with rather wide angles. Conidia ellipsoid to globose, vio 

 let or smoky, 17-18 x 22-24 ^i. 



44. Conidiophores and conidia, 1/12. 



Peronospora lepidii (McAlp.) Wilson. — On the leaves and 

 stems of Lepidium. Causes a dense white growth with more or less 

 indefinite boundaries. Conidiophores, 130-223 x 4-9 /x, erect, 3-8 

 times branched, ultimate branches arising at acute angles about 

 3-8 /x; conidia ellipsoidal or nearly globose, 18-35 x 15-23 /x. 



45. Conidiophores and conidia, 1/12. 



Peronospora parasitica (Pers.) de Bary. — On leaves and stems 

 of most Cruciferae, among which are the following economic forms ; 

 cabbage, cauliflower, radish, collards, turnips and horse-radish. 

 Diseased parts are covered with a dense white fungus growth and 

 frequently hypertrophy. Conidiophores densely branched, the last 

 branches very slender and arising at acute angles, 200-300 x 24-27 fx ; 

 conidia elliptical to globose and 12-22 x 24-27 /x, hyaline or nearly 

 hyaline. 



46. Infected leaf of radish. 47. Conidiophores and conidia, 1/12, 



