52 



LONOE\'ITV OF C'ONIDIA AND AS( 'OSPOKES. 



'I'lic Iciiiil li (»r t iiiic 1 1 ml con id i;) i-claiii (licir |m»\v('1- Io nci-niiiialc 

 will doubtless vary willi Ilic condilioiis under wliicli (lie spores 

 ant kei»t. Spores from hark eolleete<l in late summer and kept 

 dry at ordinary room temperature, j^crminated readily for four 

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

 Material exposed onl of dctoi-s and lliat kept moist and at about 

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

 after four months earlier tests not liaving been made, 



GERMINATION OF CONIDIA AND ASCOSl'ORES IN DIFFERENT MEDIA. 



Itotli kinds of spores germinale in a decoction of cliesi nut bark, 

 in rice broth, etc. Ascospores germinate in sj)ring water, the 

 conidia do not. 



EFFECT OF TEMPERATIfRE ON (JERMINATION. 



Conidia germinate best at a temi)erature of (5(1 degrees F., an<l 

 divtinctly less rapidly at temperatures 10 degrees above or below 

 this point. 



Ascospores germinate best at a temperature of about 70 degrees 

 ¥., 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 germinale readily after at 

 least moderale freezing. These facts indicate (lia( (he ascos- 

 l>ores m;iy l)lay a more im]»or(an( i>ar( in causing inf'eciion under 

 certain condilions, than has been commonly attributed to them. 



The effect of extremely high and low temperatures on spores 

 has not yet been completely inv(^stigated in our laboratory. 



EFFECT OF TEMt'EKATlTtK ON EARLY (JROWTII. 



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

 perature for gei-mination. In a nutrient solution of boiled chest- 

 nut bark, the ascospores will send (»ut a length of mycelium 10 

 to 15 times the spore length in tlie tii-st 24 liours at 70 degrees F., 

 which becomes an indefinitely large mass of mycelium in tAVO 

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

 first day, and 15 times this in five days. 



