THE PARASITIC EXOASCEAE. 



165 



Exoascus deformans (Berk.) causes the " curl disease " of the 

 peach (Persica vulgaris), and may inflict great injury. The 



Fig. 60. — Exoascus minor. Curl disease of Cherry. 



mycelium hibernates in bark, pith, and medullary rays of twigs, 

 so that it reappears each year. An Exuascus, which occurs 



Fig. (il. — Exoascus dej'or^nans. Comparison of normal section of leaf of Pvv,nus 

 Persica with a hypertrophied one, B ; in the latter the mycelial hyphae have 

 been slightly shaded. The sections are from different parts of the same leaf, and 

 are drawn with the same magnification. (After W. G. Smith.) 



on the almond {Amygdalus communis)^ resembles Ex. deformans 

 so closely that they are now regarded as the same species. 



