PSALLIOTA CAMPESTRIS 411 



come from monosporous basidia and which from bisporous basidia. 

 If one were to plot out a curve showing the variations in size of 

 a large number of spores of a single Cultivated Mushroom, one 

 would find that the curve would have two peaks. 



In a Cultivated Mushroom, the spores of the monosporous 

 basidia have a volume of about twice that of the spores of the 

 bisporous basidia. This is associated with the following facts. 

 The basidium-bodies of the monosporous and bisporous basidia 

 are equal in size (vide infra, Fig. 147) and, before the formation 

 of the spores, are equally filled with protoplasm. This protoplasm 

 is eventually all poured into the spores (with the probable exception 

 of a very thin lining layer), and the spores become stuffed with it. 

 Where there are two spores on the basidium, the protoplasm is 

 equally divided and, where there is only one, it is undivided. The 

 volumes of the spores on the monosporous and bisporous basidia 

 are correlated with the lelative amounts of protoplasm which the 

 spores are destined to contain. 



It seems very probable that the behaviour of the nuclei is 

 different for monosporous and bisporous basidia on the same 

 hymenium of a Cultivated Mushroom, and different also for the 

 trisporous and quadrisporous basidia of a Wild Mushroom. This 

 is a matter which invites cytological investigation. 



The complete emptying of the contents of a basidium-body 

 (with the probable exception of a very thin lining layer necessary 

 for maintaining turgidity) into the spores, whilst these are ripening, 

 is a phenomenon which occurs not merely in Psalliota campestris 

 but quite generally in Basidiomycetes. I have observed it in a 

 large number of species. If, therefore, one finds a spore-bearing 

 basidium only partially empty, one may be quite sure that the 

 spores, although of full size and partially or completely pigmented, 

 are not yet fully ripe, and that a stream of protoplasm is still pass- 

 ing into them through the fine necks of the sterigmata. This is 

 a fact that ought to be borne in mind by all cytologists when 

 studying nuclear behaviour in connection with basidia. 1 



It has been shown that the relative size of the spores of mono- 

 sporous and bisporous basidia in a Cultivated Mushroom is directly 

 1 CJ. Chap. I, pp. 27-29. 



