Dec, 1909.] 



SOME APPLE DISEASES. 



117 



west as Michigan. It is not so destructive as the scab, but 

 often causes otherwise perfect fruit to go as seconds. It is 

 found on abnost every variety of apple, but the Bald\\'in is 

 especially susceptible. The 

 disease appears about the 

 middle of August. At this 

 time it may be seen as spots 

 of a deeper red on the col- 

 ored surface of the apple 

 and of a darker green on the 

 lighter portion. As the sea- 

 son advances, the spots be- 

 come more prominent. They 

 usually become slightly 

 sunken, and on the red 

 surface the color often 

 changes to brown or black 

 (Fig. 7). The tissue be- 

 neath the spot is rendered 

 brown and corky to a depth 

 of several cells (Fig. 8). 

 Cold storage seems to check 

 the development of the 

 spots, but in cellar storage 

 they often become more 

 sunken and spread deeper into the tissue of the apple. 



[Microscopical studies have 

 shown that a particular 

 fungus is always present in 

 these spots. The fungus in 

 question has been found to 

 be a species of Cylindrospo- 

 rium. In the early stages of 

 the diseases it has made but 

 scant development, but later 

 it forms a firm fungus mass, 

 from the upper surface of 

 which sporophores and spores 

 are produced (Fig. 9). The 

 spores are long, thread-like and from one to five celled (Fig. 10). 



Fig. 8.— a. section thru a fruit spot. The 

 corky cells beneath the epidermis are shown 

 above, while below are seen the brown and 

 withered cells produced in the later devel- 

 opment of the spot. The fungus can be 

 seen in the pocket in the center. 



Fig. 9.— a sectifin thru' a fruit spot 

 showing a pustule or fruiting body. 



