202 



DISEASES OF CULTIVATED PLANTS 



the leaves are full-grown, under the form of brownish patches 

 which generally follow the course of the larger veins. The 

 leaves fall long before they are dead, owing to the mycelium 

 of the fungus passing into the leafstalk, and cutting off the 

 supply of food and water. Minute spore-clusters are formed 



FIG. 56. Gnomonia veneta. i, a diseased plane leaf, somewhat 

 reduced ; 2, conidia, highly mag. 



along the course of the veins on the under surface of the leaf. 

 This disease was considered to be due entirely to Gloeo- 

 sporium nervisequum (Sacc.). Klebahn, however, has recently 

 worked out the life-history of the fungus, and shows that the 

 Gloeosporium is but a conidial form of an ascigerous fungus 



