2oo DISEASES OF CULTIVATED PLANTS 



numerous minute, erumpent perithecia situated on large dis- 

 coloured patches. The mycelium of the conidial form spreads 

 rapidly in the tissues of the leaf and passes into the leafstalk, 

 cutting off the supply of food, consequently the leaves are 

 killed early in the season, and as in all such cases where 

 leaves are killed early in the season through lack of food, 

 remain hanging on the tree throughout the winter, and even 



Fig. 54- Gnomonia trythrostoma, 

 i anch with persistent, drooping, 

 dead leave 



the following season after the new Leaves have appeared. 

 The fruit is also attacked at times, when it becomes distorted 

 and ripens unevenly. During the winter months the higher 

 or ascigerous form of fruit is developed on the dead, hanging 

 leaves. The spores produced by this form of the fungus 

 infect the young leaves the following season. 



The perithecia of the conidial form are very minute, and 

 burst through the epidermis of the leaf, ostiolum not elon- 

 gated ; sporophores branched ; spores filiform, hyaline, slightly 

 curved, terminal or originating from the nodes of the sporo- 



