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SOME NOTES UPON ECONOMIC PERONOSPORE^l FOR 1889 IN NEW 
JERSEY. 
By Byron D. Halsted. 
Early in the season as announced in the Botanical Gazette for June, 
page 152, a peronospora was found upon cucumber leaves growing under 
glass here in JSew Brunswick. The disease assumed a violent form, and 
in the course of a few weeks all the vines were dead. Squash seed was 
afterwards sown in the same bed to determine whether the peronos¬ 
pora would develop upon this near relative of the cucumber. In the 
meantime the mildew, which seemed to be new, was studied; the method 
of germination by zoospores, and other points were determined and 
specimens with drawings were afterward sent to Dr. Farlow. 
An account of this peronospora was given by Dr. Farlow in the 
Botanical Gazette for August, page 189, in which it was stated that the 
same species had been found a few mouths before in Japan, and that it 
was Peronospora Cubensis , B. & 0., first found in Cuba on Gucurbi - 
tacece , and described several years ago. 
Leaving aside the interesting fact of the widely separated points 
where this fungus has been found the readers attention is called to the 
economic side of the question, for not only were the squash leaves of 
plants growing in the liot-bed infected, but squash and pumpkin vines 
in various parts of the State were seriously attacked. The writer made 
it a point to look for this mildew as he visited various counties, and in 
all cases it was met with, and in some instances was so abundant as to 
discolor and destroy the leaves before they had attained full size. 
The squash plant, from its habit of growing horizontally upon the 
ground and bearing large, widely separated leaves, is an easy one upon 
which to study the development of this fungus. It was never found 
upon the young leaves, but it followed some distance after and became 
manifest, for example, upon the fourth or fifth leaf from the extremity 
of the vine. The greenisli yellow patches are first seen, and these are 
small and irregular in shape, being bounded by the veinlets. The spores 
are borne upon the under side of these patches and when mature are 
remarkably dark in color. This color is much darker upon the squash 
than the cucumber, and there are other differences which would be 
amply sufficient to warrant a varietal name if it was not evident from 
the hot-bed experiment that the differences are very probably entirely 
due to the intluence of the host. During another season, should this 
pest return, it is hoped that other experiments will be made to deter¬ 
mine more fully the habits of this fungus. As yet no oospores have 
been found. It should also be said that the attacks of this peronospora 
upon the cucumber were not confined to those growing under glass, but 
instead almost ruined some large fields of this plant. From the fact 
