98 SEVENTEENTH REPORT. 



fungiis begins to fruit ou the surface aud becomes mature the ac- 

 tion of the parasite seems to be checked and the host begins to 

 form a thin layer of cork cells about the lesion. 



This seems to be resistant to the fungus action as the lesions are 

 never more than 2-3 mm. deep. This corky layer is more apparent 

 after the fruit is withered and dry, when the epidennis may be 

 peeled off and the bare cavity will be found underlaid with a tough 

 layer of corky cells. 



When seen in vertical sections the fungus growth appears to be 

 on the surface with a shallow cavity beneath, but this is not really 

 the case as the epidennal tissue is entirely destroyed and the fun- 

 gus penetrates as far as the bottom of the cavity. The formation 

 is due to the fact that the web of mycelium hardens and dries on 

 the surface by the evaporation of the gummy material's volatile 

 portion and a sort of ciiist forms covering cavity beneath. 



The threads of the mycelium do not seem to penetrate the cells 

 but are found closely pressed along them. The cells, three or four 

 layers back, in young lesions show traces of gradual disintegration 

 by their broken walls, but the fungus apparently cannot actually 

 penetrate the cell wall. 



AGENTS OF DISTRIBUTION. 



The methods of transmission of the disease may be mauy as the 

 spores are produced in great numbers on the fiuit and to some ex- 

 tent on the leaves and petioles. 



The conidia are ver}- easily detached and may be blow about by 

 the wind to some distance so that this seems likely to be the most 

 common means of dissemination. 



The human agency is also a factor as the ]»ickers may carry large 

 numbers of spores on their clothes, shoes, and hands. Insects may 

 also play a small part in the spread of the disease, and the splash- 

 ing of water during heavy rains would account for further infection. 



The fungus probably winters over in the trash of the year pre- 

 vious, since the stems, leaves, and pickles ])lowed imder would 

 carry a large amount of infectious material to reproduce disease 

 during the following season. 



The (piestion of transmission by seed is an open one but there 

 is a possibilily that during the process of removing the fleshy ytov- 

 tion of the fruit many spores might become attached to the seed 

 coats. 



RESISTANCE OF THE ORGANISM TO FUNGICIDES. 



As no work had been done on the disease except that by Frank, 

 it was decided to attempt to discover whether the copj^r sprays 



