222 AGRICULTURAL EXPERIMENT STATION. [J;in. 



same fungus; and this fact makes it obvious that spinach 

 lields should be kept scrupulously free from pigweed, 

 which, if allowed to grow, may afford a favorable breeding 

 place for the mildews 



The Grape-v^ine Mildem' {Plasniopara viticola (B. & 

 C.) Berl. & de T.) might be expected to attack also our 

 native species of Ampclofsis, the Virginia Creeper, and 

 the species from Japan, now commonly planted under the 

 name of Japanese or Boston ivy, since the species of 

 Ampclopsis are so nearly related to the grapes that they 

 are placed by some writers as a subdivision of the genus 

 Vitis, wliich includes the true grapes. Its occurrence on 

 the Virginia Creeper has been reported from various locali- 

 ties ; but, so far as I know, the Japanese ivy {A. Vcitchii.) 

 has been only once reported as its host.* It is therefore 

 worth while to note the occurrence of the mildew on the 

 latter plant, in October last, in Amherst. The fungus was 

 well developed, almost as luxuriant as on the grape, and 

 its summer spores, always varying considerably in size, 

 showed an unusually wide range of dimension. The 

 leaves attacked were large and strong, and the fungus 

 threads penetrated their tissues very thoroughly, though a 

 careful examination failed to discover the resting spores. 

 The damage to the vines, which were well established and 

 vigorous, was not important, and the chief interest of the 

 facts noted lies in the possible danger to grape vines in the 

 proximity of wild or cultivated Ampclopsis plants, which 

 may serve as an important source of infection, if their 

 presence is overlooked. The simplest precaution is, natu- 

 rally, that of rigorously excluding the species named from 

 the neighborhood of grape vines. 



Two closely related fungi appeared to a considerable 

 extent on a plot of purple-topped white turnips on the Sta- 

 tion grounds in September last. They were the Downy 

 Mildew {Pero7iosj)ora parasitica (P.) Tul.) and the 

 White Rust {Cystopus candidus (Pers.) Lev.) of cru- 

 cifcroiis plants. They often appear together, and some- 

 times do considerable damage. Any field on which they 



• Journal of Mycology, 1889, p. 202. 



