492 RESEARCHES ON FUNGI 



of one of the Poplar trunks at a height of about 4 feet from the 

 ground and, as the tree was somewhat exposed, to make successful 

 observations I found it necessary to shield the fruit-bodies from the 

 wind with my overcoat. On directing the beam of light horizontally 

 in front of the group of fruit-bodies and looking across the beam 

 vertically downwards or somewhat obliquely toward the ground I 

 distinctly saw clouds passing through the light and being broken up 

 and dispersed by air-currents. From December 24 to December 28 

 I visited the fruit-bodies nightly and, on each occasion, the lamp 

 revealed clouds of spores coming away from the pilei. Preparations 

 for my departure from England on December 30 then brought the 

 observations to a close and I was therefore unable to determine 

 the exact length of the spore-discharge period of the fruit-bodies 



investigated. 



The observations just recorded show that the fruit- bodies of 



Collybia velutipes which came under my observation were liberating 



spores for six days. As in the investigation of Pleurotiis ostreafus, 



it was found that spore-discharge was more active on warm nights 



than on cold, and that when the air was still it was much easier 



to detect the spore-clouds than when there was a decided breeze. 



The temperature for each observation was taken with a thermometer 



set near the fruit-bodies, and the thermometric data were practically 



identical with those already given for December 23-28 in the Table 



on p. 488. The lowest temperature for any observation was 34° F. 



on Christmas Eve ; but, even on that occasion, the fruit-bodies 



continued to produce spore-clouds, although relatively thin ones. 



From the hand-lamp observations just communicated we may 

 conclude that the fruit-bodies of Collybia velutipes, like those of 

 Pleurotus ostreatus, are so organised that, even when the temperature 

 of the air is only a little above the freezing-point of water, they 

 may freely carry out their one great function of producing and 



liberating spores. 



It used to be thought that fungi necessarily cease all growth 



activity at, or a little above, the freezing-point of water. However, 



we now know that this is not always the case ; for, in 1909, I ' 



showed that the fruit-bodies of Daedalea unicolor, Lenzites betulina, 



1 A. H. R. Buller, these Researches, vol. i, 1909. pp. 124-126. 



