VINE MILDEW. 509 



foliage. It also attacks fruit trees, but seems to 

 prefer the vine. It can be destroyed by carefully 

 gathering the leaves which are rolled, and burning 

 them. This will kill the larva, and prevent further 

 multiplication. 



2. Fungi. (1) Vine Mildew — Oidiiim Tuckeri : 

 This is a fungus appearing upon the under surface 

 of the foliage, resembles a white powder, and is very 

 rapid in its propagation. It often spreads upon, and 

 destroys, the fruit. If not arrested, it will ultimately 

 ruin both the foliage and the young wood. 



As fungus generally attacks vegetation when it is 

 inactive, we must look to some previous cause. Cer- 

 tain waiters have considered the oidium as epidemic; 

 but it is probably endemic. It seems to depend 

 upon a certain condition of the plant, and the fun- 

 gus is really but the consequence. This is to be 

 proved from the observations of so many cultivators 

 of the grape, who describe it as attacking the vine 

 in fine weather, after a cold or wet season. There 

 seems to be no doubt that its appearance is due to 

 a stagnation of the sap, resulting from a sudden 

 transition from warmth to cold in the atmosphere. 

 Among the instances of injury by it was one in 

 which the vines were situated in a cold grapery, 

 and a hail storm having broken some of the 

 glass, the change in the temperature was imme- 

 diately followed by mildew upon the vines. There 

 43* 



