PLATE III 
Fig. i.— Cysiopus candidus on Lepidium virginicum. This plant was chopped out 
of the frozen ground on February 22, 1911, and brought into the greenhouse. There 
days later white pustules of Cystopus candidus began to appear on the leaves. 
Fig. 2.— A, The two leaves at the left show the amount of sporulation of Peronospora 
parasitica on leaves of Lepidium virginicum; B, the two leaves at the right show Cystopus 
candidus fruiting on leaves of Capsella bursa pastaris . The pustules developed from 
mycelium alive in the plants in the winter of* 19x1. 
Fig. 3.— Peronospora viciae on Vida sepium . A systematic infection of the downy 
mildew collected on April 15, 1914, in the District of Columbia. This plant was 
badly infected when coming through the ground. 
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