PSATHYRELLA DISSEMINATA 



51 



tuberant at all. It is clear that the basidia as a whole are tetra- 

 morphic. The overlapping in the time of development is obvious. 

 The spores of the first-generation basidia are fully pigmented and, 

 therefore, nearly ripe and about to be discharged. The spores of 

 the second-generation basidia have not only already attained full 

 size but are undergoing pigmentation. The spores of the third- 

 generation basidia have attained full size but are still colourless. 



Fig. 29. — Psathyrella disseminata. Transverse section through 

 the hymeniuni during its development. There are four 

 generations of basidia : a, the first, bearing black spores ; 

 b, the second, bearing brown spores ; c, the third, bearing 

 fully-grown colourless spores ; and d, the fourth, bearing 

 rudiments of spores, p, a paraphysis. Magnification, 

 687. 



The spores of the fourth-generation basidia are only just beginning 

 to develop and have not yet attained to full size. This overlapping 

 in the time of development of successive generations of basidia 

 contrasts very strongly with what occurs in the hymenium of the 

 Panaeolus Sub-type, for in Panaeolus campanulatus, Stropharia 

 semiglobata, Psallioia campesiris, etc., one generation of basidia 

 (except of course the first) never begins to develop spores until the 

 spores on the basidia of the preceding generation have been dis- 

 charged. The paraphyses p pin Fig. 29 appear as oval or quadratic 

 cells, and one can perceive that they are just about the right size 

 to maintain sufficient space between adjacent spore-bearing basidia. 

 At the same time it is evident that they support the basidia in their 



