220 



RESEARCHES ON FUNGI 



measured 11-65 yx in diameter were found to fall, immediately 

 after their discharge, at the rate of 6-07 mm. per second.^ Using 

 this fact as a guide, I think it probable that the rate of fall of the 



undried spores of Coprinus 

 sterquilinus varies from 6 to 

 8 mm. per second. But, after 

 leaving the gills, the spores, if 

 carried off by the wind in 

 moderately dry air, would dry 

 up within a few seconds and 

 then would fall much more 

 slowly. In any case, I think 

 there can be no doubt that, 

 on account of their great size, 

 the spores of Coprinus sterqui- 

 linus are not carried far by 

 light breezes. But this is of 

 no serious disadvantage, as 

 all that is required for suc- 

 cessful dispersion is that the 

 wind should carry the spores 

 away from the fruit-body a 

 distance sufficiently great to 

 permit of their settling on 

 grass along with which they 

 may be swallowed by grazing 

 horses. Since, under natural 

 conditions, grass is usually 

 present in the immediate 

 vicinity of horse-dung masses 

 upon which fruit-bodies have developed, the spores, although 

 coming rapidly to earth after their liberation, are likely to lodge 

 upon it. Wood-destroying fungi which live on trees usually have 

 relatively small spores, and this makes it easier for the spores to 

 settle in those high locations where invasion of the wood by their 



Fig. 93. — Comparative size of basidia. A, 

 a basidium of Psalliota campestris (cul- 

 tivated form) ; B and C, two basidia of 

 Coprinus sterquilinus. The volume of 

 the basidium and two spores of A is 

 only about equal to the volume of a 

 single spore of B or C. In A and B, 

 each right-hand spore, in preparation 

 for violent discharge, has just excreted 

 a liquid drop. The size of the drops is 

 proportional to the size of the spores. 

 Magnification, 970. 



^ These Researches, vol. i, 1909, p. 173. 



