82 PLANT DISEASES 



extending to other maize-growing countries. So far as is 

 known, it is at present confined to Java. 



Raciborski, Ber. deutscken Bot. GeselL, vol. xv. p. 475, 

 figs. 1-4 (1897). 



ASCOMYCETES 



GYMNOASCACEAE 



Leaf Curl 



(Exoascus deformans, Fckl.) 



This parasite is very destructive to the foliage of the 

 peach ; the leaves of the almond are also sometimes 

 attacked. The disease, which is very widespread, is 

 popularly known as 'leaf curl,' or simply as 'curl,' owing 

 to the fact that diseased leaves become much curled, dis- 

 torted, and thickened, and of a pale yellowish green, then 

 rosy or purplish colour; finally the convex portions of the 

 diseased leaves become covered with a very delicate whitish 

 bloom, which presents a minutely velvety appearance 

 when seen through a pocket-lens. This appearance is 

 caused by the fruit of the fungus, which bursts through 

 the cuticle, and comes to the surface of the leaf for the 

 purpose of enabling the spores to be diffused. 



The young shoots are also often more or less swollen and 

 distorted by the fungus, whose mycelium is perennial in 

 the branches, and each season passes into the leaf-buds, 

 which consequently contain the mycelium of the fungus 

 in their tissues when they expand the following spring. 

 New cases of infection must necessarily arise from the 

 presence of spores floating in the air and alighting on 



