174 BOARD OF AGRICULTURE. [Jan., 



through these breathing spores of the leaf — often half a dozen 

 from a single "pore " — and branch so as to appear like a miniature 

 tree. Upon the tips of these branches the spores are rapidly 

 formed. It is the vast multitude of these little branched tops, 

 with their clear, transparent spores, which gives the white, frosty 

 appearance of the infected spots as seen by the naked eye. The 

 contents of the spore, a few hours after it is ripe, divide into from 

 six to ten oval bodies, which soon rupture the spore-wall and 

 escape, each provided with two little hair-like processes, by means 

 of which it can rapidly move about. Here, then, we have each 

 spore producing a number of moving bodies, which, after finding 

 a suitable locality, germinate and reproduce the millions in a new 

 place, and it may be on another plant. 



Besides these non-sexual spores, just described, there is another' 

 kind always formed within the tissue of the grape plant, and is 

 sexual, as it is necessary that the contents of two different threads 

 should mingle in order that one of these spores may arise. These 

 spores are large, and covered with a thick cell-wall, slow in their 

 formation in comparison with the exceedingly rapid development 

 of the aerial, non-sexual spores. They are only produced late in 

 the season, and serve the special purpose of carrying the mildew 

 over the winter. They germinate in the same way as the smaller 

 spores, by producing a number of motile bodies, which, when find- 

 ing their way to the grape plant, repeat the trouble of the previous 

 year. 



This mildew makes its appearance any time from the first of 

 June to the last of September, depending very largely upon the 

 state of the weather — a succession of warm rainy days_ being the 

 most favorable for its development. I have often been asked what 

 varieties are most susceptible ; but the question cannot at present be 

 answered. The strong thick-leaved varieties, like the Concord, 

 appear to be less affected, while some tender thin-leaved varieties 

 are almost ruined. Although this mildew is peculiar to America, 

 it flourishes upon foreign vines, when brought to this country, 

 " even more luxuriantly than on American species." The mildew 

 of Europe, which, at times, has proved so disastrous in the vine- 

 yards of Madeira, is a fungus of a very different kind from this, 

 and demands separate consideration, as we have it also. 



Flowers of sulphur, used with a bellows, early in the season, 

 when "an ounce of prevention is worth a pound of cure," followed 

 by repeated dusting, as circumstances of weather, etc., decide, is 



