126 RESEARCHES ON FUNGI 



to be at their best in the middle of an English winter, from 

 which fact it seems justifiable to conclude that cold weather is 

 favourable to their development. 



The effect of high temperatures upon spore-discharge has been 

 investigated only in the case of Lenzites betulina, The fruit-body 

 to be tested was first determined to be freely shedding spores by the 

 beam-of-light method. It was then pinned to a cork fixed to a glass 

 plate, after which the plate was placed over a beaker, so that the 

 fruit-body assumed its normal orientation (cf. Fig. 37, p. 97). This 

 beaker with its cover, and another similar but uncovered beaker, were 

 then placed in the incubator, the air of which had been raised to the 

 desired temperature. After from thirty minutes to two hours, when 

 doubtless the fruit-body had assumed the temperature of the incu- 

 bator, the plate was quickly taken from the first beaker and set upon 

 the second. The air within the second beaker before this operation 

 was, of course, free from spores, whereas that of the first might still 

 have contained spores which had been liberated by the fruit-body 

 before this had become heated. After another fifteen or thirty 

 minutes, the second beaker was removed from the incubator and 

 immediately examined by the beam-of-light method. If spores had 

 been liberated into it, they could easily be seen floating in the air. 



As a result of experiments of the kind just described, it was 

 found that the discharge of spores took place slowly at 29° C, but 

 not at 33°, 43°, or 46°. The fruit-bodies, however, were not killed by 

 exposure for forty-five minutes to these high temperatures, for when 

 they were afterwards placed in a moderately heated room, in the 

 course of several hours they recovered and shed spores again in 

 abundance. 



The modes of action of extreme cold and of extreme heat are 

 doubtless different. Extreme cold must slow down the metabolism 

 and hence prevent spore development. No injury in the case of 

 Lenzites, Dsedalea, and other similar fruit-bodies growing on logs, 

 results from a long exposure to very low temperature, e.g. from — 15° 

 to — 40° C, such as occur often for weeks together in the course of 

 winter at Winnipeg. As soon as a fruit-body is warmed sufficiently, 

 spore-fall begins anew. Fruit-bodies of Lenzites betulina, Stereu m yu r- 

 pv/reum, and Schizophyllum commune were gathered from a Avood- 



