Brooks : The Fruit Spot of apples 443 



An examination of cross sections of these showed that numerous 

 U-shaped cavities had developed on their surfaces and that where 

 these were present the layer of conidiophores was wanting. These 

 cavities were bordered by rather dense layers of mycelium and 

 contained parallel erect hyphae with thinner-walled and almost 

 isodiametric cells that in some cases gave a suggestion of pre- 

 sporogenous tissue. 



In agar cultures the conidia were produced beneath the sur- 

 face of the agar. One spore would be produced and pushed aside 

 to give way to a second, and this followed by a third and so on 

 indefinitely (plate 35, figure 2). In young cultures nearly all of 

 the mycelium was beneath the agar, later a mass of coarse aerial 

 hyphae developed (plate 32, figure 5). In such cases a black 

 stromatic layer was formed just beneath the surface of the agar. 



Chlamydospores were common in all old cultures. 



Conidia germinated rapidly in hanging-drop cultures (plate 



34, figures i, 2, 3). Under similar conditions chlamydospores 



germinated as shown in plate 35, figure 4. Each cell of the 



stromatic mass in old cultures seemed to have the power to send 



°ut hyphae when transferred to a fresh medium (plate 35, fig- 

 ures 5, 6). • 



The conidia from very old cultures did not germinate but the 

 chlamydospores and thick-walled hyphae retained their vitality a 

 on g time. Germination was secured from chlamydospores in an 

 a gar culture that was twenty-six weeks old and in which the 

 Medium had been hard and dry for more than five months. 



The fungus developed as well in cultures at a temperature of 



! 5 degrees as at 20 degrees but made a poor growth at 30 degrees. 



was killed by an exposure for five days to a temperature of 37 



e grees. It was evidently not injured by prolonged exposure to 



0W tem peratures, as it was repeatedly isolated from apples which 



ad °een in cold storage for several months. It was also obtained 



m cultu re from an apple which had been exposed for eight days to 



a e mperature varying from — 28 degrees to — 6 degrees C. 



Relation of the 



NUTRIENT 



The fungus grew best on acid media and was very sensitive to 

 SUgar ,n culture solutions. In most culture media that lacked 



