LIFE HISTORY OF FUNGUS. 21 



charge of the spores and form one of the most characteristic features 

 of the disease. The spores disappear from the tip of the pustules 

 after a time. Rain or dew may wash them away or insects rub 

 them off. The empty sori remain behind and have a sooty, black 

 appearance. 



The time elapsing between spore germination on a fruit and the 

 ripening of the first spore crop differs with the season from three or 

 four da}^s to a week. In hot days of August the cycle is completed 

 with great rapidity. In one and the same spot on a fruit spores may 

 be forming at the center, while a quarter of an inch farther out the 

 pustules have not yet begun to develop. 



The foregoing description of the growth of the fungus pertains to 

 the development on apples still on the trees. Spores inoculated into 

 apples after they have been picked will give rise to similar phenomena. 

 The rate of growth of the fungus and the formation of spores will 

 depend entirely on the temperature and moisture conditions under 

 which the inoculated apple is kept. 



The spores of Glmosporium fructigenum Berk, germinate on grapes 

 when they are almost or quite ripe (Southworth, 1891). The bitter 

 taste which follows the attack of this fungus on apples is absent in 

 diseased grapes. Hence the more common designation of "ripe rot" 

 for the same disease of the grape. On white grapes small reddish- 

 brown spots appear, which spread and become darker as they grow 

 older, until the spots have an almost purple center with a bright brown 

 border. The pustules on the grape are at first white, then darker, 

 until they are almost black. The spores are flesh-colored. The berry 

 ultimate^ dries up, but does not turn black. Dark-colored grapes 

 how no color changes when attacked. 



THE CONIDIA 



The spores of Gloeosjx>rkun fructigenum Berk, produced in the 

 soil, and commonly called conidia, are pinkish- colored en masse. This 

 color varies from a light fresh pink to a darker reddish pink. a When 

 highly magnified they have a very delicate light-green color. This 

 color is quite distinct, and it seems strange that of manj^ observers 

 Alwood (1894) seems to be the only one to recognize this greenish 

 color. Clinton (1902) states that the conidia are colorless, while Miss 

 Southworth (1891) says that they are hyaline. 



In size and form the conidia are extremely variable. The great 

 variability in these respects has probably been responsible for the 

 difficulties which many observers have labored under when it came to 

 deciding which of the several fungi causing similar diseases of fruits 



a One of the writers noted apples which had been inoc^ated in the laboratory and 

 bore only cream-colored spore masses. The spores seemed to be perfectly normal in 

 other ways. 



