RATE OF DEVELOPMENT OF INDIVIDUAL SPORES 55 



after attaining full size they remain on the sterigmata for periods 

 varying from 43 minutes in the first species to 1 hour and 10 minutes 

 in the third. Furthermore, the spores of Calocera cornea and of 

 Psalliota campestris both take 40 minutes to develop to full size ; 

 yet those of the former take only 40 further minutes for their 

 ripening processes whereas those of the latter require more than 

 7 hours. It is to be noticed for the species investigated, however, 

 that the spores which grow to full size in the least time, namely, 

 those of Collybia velutipes, ripen in the fastest time, while those 

 which grow to full size in the maximum time, namely, those of 

 Coprinus sterquilinus, take the longest time for ripening. Among 

 the Leucosporae, it is to be noted that the spores of Russula 

 cyanoxantha, which are warted, take much longer to grow to 

 full size than any of the smooth- walled spores. 



The ripening of a spore involves a good many processes, among 

 which one may perceive the following : (1) the transference of 

 protoplasm from the basidium-body through the sterigma into the 

 spore-lumen, a process which continues long after a spore has 

 attained full size and which leads to the emptying of the basidium- 

 body ; (2) frequently, the division of the nucleus which has entered 

 the spore through the sterigma ; (3) chemical changes, such as the 

 conversion of glycogen into non-glycogenous products (observed 

 in Coprinus sterquilinus} ; (4) the frequent formation of a thick, 

 pigmented inner wall or endospore ; and (5) a preparation for 

 spore-discharge by some alteration at the hilum, of which the excre- 

 tion of a drop at the hilum a few seconds before spore-discharge 

 is a very obvious sign. It is not surprising that all these changes 

 should take a good many minutes or even hours for their accom- 

 plishment. 



Already, in a section of Chapter I, a detailed account was given 

 of the development and discharge of the spores of Calocera cornea. 

 It will be of interest in this place to give some corresponding details 

 for Stropharia semiglobata which, unlike the Calocera, has highly 

 pigmented spores. The time scale in the following Table will 

 be regarded as starting at zero. The mean times given were 

 obtained by observing the development of the spores on six different 

 basidia. 



