52 



LONGEVITY OF CONIDIA AND ASCOSPORES. 



The length of time that conidia retain their power to germinate 

 will doubtless vary with the conditions under which the spores 

 are kept. Spores from bark collected in late summer and kept 

 dry at ordinary room temperature, germinated readily for four 

 months, but three weeks later could not be induced to germinate. 

 Material exposed out of doors and that kept moist and at about 

 75 degrees F. in a greenhouse, did not give germination of conidia 

 after four months earlier tests not having been made. 



GERMINATION OF CONIDIA AND ASCOSPORES IN DIFFERENT MEDIA. 



Both kinds of spores germinate in a decoction of chestnut bark, 

 in rice broth, etc. Ascospores germinate in spring water, the 

 conidia do not. 



EFFECT OF TEMPERATURE ON GERMINATION. 



Conidia germinate best at a temperature of 00 degrees F., and 

 distinctly less rapidly at temperatures 10 degrees above or below 

 this point. 



Ascospores germinate best at a temperature of about 70 degrees 

 F., but a good percentage of germination occurs at 85 degrees F. 

 and 45 degrees F. Even at 38 degrees F. the "germination of as- 

 cospores was 25 per cent, in the first 24 hours, and reached 70 

 per cent, in three days. Ascospores germinate readily after at 

 least moderate freezing. These facts indicate that the ascos- 

 pores may play a more important part in causing infection under 

 certain conditions, than has been commonly attributed to them. 



The effect of extremely high and low temperatures on spores 

 has not yet been completely investigated in our laboratory. 



EFFECT OF TEMPERATURE ON EARLY GROWTH. 



In general the most rapid early growth is at the optimum tem- 

 perature for germination. In a nutrient solution of boiled chest- 

 nut bark, the ascospores will send out a length of mycelium 10 

 to 15 times the spore length in the first 24 hours at 70 degrees F., 

 which becomes an indefinitely large mass of mycelium in two 

 days. At 38 degrees F., the growth is about one spore length the 

 first day, and 15 times this in five days. 



