482 



RESEARCHES ON FUNGI 



possession of two fruit-bodies of Pleurotus ostreatus gathered from 

 the same log on the same day : one gathered at 1.30 p.m., at a 

 temperature of 70° F., shedding spores vigorously, which we will 

 call A, and another, just gathered, at a temperature of 32° F., not 

 shedding spores at all, which we will call B. I now reversed the 

 temperatures of A and B, A was set outside on a cold window- 

 ledge where the temperature was 32° F., while B was brought into 

 the warm room where the temperature was 70° F. After an hour 

 and a half had passed, A was brought back into the room and both 

 A and B were examined with the hand-lamp. A now proved to be 

 entirely inactive, while B gave forth spore-clouds vigorously. This 

 experiment and its results are embodied in the accompanying Table : 



The Effect of High and Low Temperatures upon the Production of 

 Spore-clouds from Pleurotus ostreatus. 



The experiment just described clearly proves that in Pleurotus 

 ostreatus spore-discharge goes on very vigorously at high temper- 

 atures, such as 70° F., but very slowly or not at all at very low 

 temperatures, such as the freezing-point of water. Doubtless, 

 under natural conditions in the open, the fruit-bodies of P. ostreatus 

 exhaust their basidia more slowly and live for a longer time when 

 the weather is persistently cold than when it is persistently warm. 



November and December Field-observations. — The next series 

 of observations shows that, in the late autumn, under natural 

 conditions, the spore-discharge period of Pleurotus ostreatus may 

 exceed a month. 



On November 23, about four feet from the ground, on the 

 moribund trunk of one of the severely trimmed Poplars in the 

 garden, I found several P. ostreatus fruit-bodies (Fig. 199) which had 

 attained scarcely a quarter of their full size and which, therefore. 



