FAI CK'S THEORY OF RADIOSENSITIVITY 143 



and increases the number of spores liberated per minute ; ^ and, 

 when a fruit -body confined under a bell-jar or in a closed chamber 

 is heated by radiant energy coming from a lamp, etc., no doubt 

 convection -currents come into existence and assist in dispersing the 

 spores. However, under natural conditions, there is no reason to 

 suppose that the pilei of Coprini are dependent on direct sunlight 

 for success in producing and liberating their spores, and it seems 

 certain that the wind, which easily swamps small convection-currents 

 formed about a pileus exposed to the sun, is the chief, and by 

 far the most important, agent in spore-dispersion. 



1 Cf. these Researches, vol. i, 1909, pp. 123-127 ; vol. ii, 1922, pp. 56-57 ; and 

 tliia volume, chap. xiv. 



