Entomological Xotes. 323 



berof Zoospores, generally from five to fifteen, each of which is 

 capable, under favorable conditions of producing a new myce- 

 lium ur. 1 spores. Like the corresponding bodies in Uncinula, the 

 conidial spores are destroyed by cold. 



The winter spores of the Peronosprra are thick and tough, and 

 are produced in the interior of the grape leaves by a rather conv 

 plicated process, which, although interesting from a botanical 

 point of view, need not be described here. They fall to the ground, 

 with the leaves in the autumn, and are set free by the rotting 

 away, during the winter and spring, of the leaves in which they 

 are contained, and as the season advances they germinate, and 

 enter the nearest vines, but the details of the germination have not 

 yet been made out. The remarks already made about burning 

 the grape leaves apply also in this connection. The mycelium of 

 the Peronospora in the interior of the vines affected during the 

 summer may remain dormant during the winter, and start up again 

 when the warm weather returns. Just how much harm the Pero- 

 nospora does to the grape vines is not easy to decide. I have, on 

 a previous occasion, expressed the view that it is not unlikely 

 that the harm done has been exasperated, because the fung-us never 

 attacks the berries, and it does not cause the leaves to shrivel and 

 dry up until comparatively late in the summer, when, as some 

 say, their room is better than their company, for what is especially 

 needed is, that there shall be plenty of sunlight to ripen the grapes, 

 which is not the case when the foliage is luxuriant, and covers up 

 the branches. Whether the shrivelling; of the leaves in the latter 



O 



part of August permanently injures the vines, and injures the crop 

 is a point to be settled, not by the botanist, but empirically by 

 the grape grower, and as far as can be learned, on this point 

 opinions differ. 



My object in describing the two principal blights on the Ameri- 

 can grapes has been to show that an accurate and scientific knowl- 

 edge of the causes of diseases in plants requires a careful 

 microscopic study, and that such study is not without definite and 

 practical results. The time has passed when the labors of bota- 

 nists should be considered of interest only to special students of 

 science. From them the farmer may learn certain facts of which 



