BASIDIA AND THE DISCHARGE OF SPORES 29 



total volume of the spores which it produces. In the cultivated 

 form of Psalliota campestris the basidia are all of about the same 

 size. Most of them produce two spores, but exceptions to this 

 rule are not infrequent, for it is not difficult to find basidia which 

 have but one sterigma and one spore only. The volume of the 

 spore of a monosterigmatic basidium is twice that of one of the 

 spores of a disterigmatic. A monosterigmatic basidium is equal 

 in size to, and contains as much protoplasm as, a disterigmatic. 

 There is therefore as much protoplasm available for the single spore 

 of the first as for the two spores of the second. The sizes of the 

 spores are evidently adjusted to the amount of protoplasm which 

 they are destined to contain. 



In most species of Hymenomycetes, the spores take several 

 hours to mature after coming into existence. After they have 

 grown to full size, all the protoplasm of the basidium-body, with 

 the exception of a thin lining layer, flows into them. There is 

 therefore none left over which might be used for the production 

 of a second generation of spores. This is true for all basidia, so 

 far as my observations go, whatever the number of spores which 

 they produce. The whole mechanism of the basidium seems to 

 me to be adapted for the production of a single generation of spores 

 and no more. 



The Sterigma and Spore-hilum in Hymenomycetes and Gastro- 

 mycetes. Throughout the Hymenomycetes, the sterigma is well 

 developed and consists of a distinct, longer or shorter, gently 

 curved, tapering, conical body. Moreover, in all the species of 

 this great group, a hilum, from which a drop of water is exuded 

 just before spore-discharge, comes into existence in the first stage 

 of each spore's development. The hymenomycetous spore, when 

 full-grown, has a long axis which is inclined at an angle of about 

 45 to the long axis of the subjacent sterigma. Where the basidium 

 is quadrisporous, the four sterigmata are symmetrically spaced 

 about the free end of the basidium, so that the distances between 

 successive sterigmata are all equal. The spores are symmetrically 

 arranged in the same manner and all their hila are turned inwards 

 toward the basidium-axis. This beautifully symmetrical quadri- 

 sporous basidium is typical for the Hymenomycetes, and occurs 



