PANAEOLUS CAMPANULATUS 



321 



may therefore conclude that the positions of the sterigmata on 

 the end of any basidium are decided by the positions of the 

 nuclei in the basidium just before the sterigmata are formed. 



The number of sterigmata on a basidium is doubtless related 

 to the number or mode of arrangement of the nuclei derived from 

 the fusion-nucleus. Probably in tristerigmatic basidia there are 

 only three nuclei present 

 instead of the usual four, 

 while in pentasterigmatic 

 a'nd octosterigmatic 

 basidia there may be 

 five nuclei and eight 

 nuclei respectively. If 

 the fusion-nucleus 

 divided three times, eight 

 nuclei would result, and 

 this may happen in 

 octosterigmatic basidia ; 

 but how the fusion- 

 nucleus divides so as to 

 form only three nuclei 

 or just five is rather 

 puzzling. No doubt 

 light might be thrown on 

 this matter by cy tological 

 investigation. 



K&&2S8 



u n_QI^ u O^ 



FIG. 111. Coprinus echinosporus Buller. Surface 

 view of the hymenium showing plan of 

 spores which have a domino-like arrange- 

 ment, as in the lines a-b and c-d-e ; f, a 

 cystidium. The spores of the long basidia 

 have been shaded, those of the short basidia 

 left plain. The echinulations are only shown 

 at g where two spores are represented in 

 lateral view. Magnification, 440. 



We have so far dealt 



with the position of the sterigmata on individual basidia. 

 We shall now turn our attention to the position of sterigmata 

 on closely adjacent basidia. In certain species of Coprinus, 

 e.g. C. echinosporus BuUer, if one examines the hymenium in 

 face-view, one can at once observe that the spores of adjacent 

 basidia tend to have the domino-eight arrangement (Fig. 111). 

 If one had to crowd as many four-spored basidia as possible into 

 a given area of the hymenium so that the spores would not touch 

 one another, this could be done more successfully on the domino- 

 eight plan than on any other. Proof of this is best obtained by 



VOL. ii. y 



