RATE OF DEVELOPMENT OF INDIVIDUAL SPORES 47 



definite size from the hilum of each spore just before discharge. 



FIG. 15. Collybia velutipes, a species with thin, smooth, colourless spore-walls, 

 which develops its individual spores very rapidly : the interval elapsing 

 between the first formation of a spore on its sterigma as a tiny rudiment 

 and its discharge is less than 1 hour (about 47 minutes). The fungus 

 has a brown velvety stipe and is often found in autumn on dead trunks of 

 trees and about stumps in Europe and North America. Photographed at 

 Scarborough, England, by A. E. Peck. Natural size. 



Normally, too, the time from the origin to the discharge of a spore 

 is very constant under the same conditions for each species : its 



