568 RESEARCHES ON FUNGI 



scribed, which grows out from bark or wood through the soil. On this 

 ozonium the fruit-bodies are eventually developed. The existence of 

 the ozonium accounts for the fact that thousands of fruit-bodies are 

 often seen coming up simultaneously on bare soil surrounding the stump 

 of a tree or covering dead roots. 



An ozonium has two functions : (1) it serves to spread the fungus 

 locally in a rapid manner, and (2) it enables the fruit-bodies to arise in 

 more suitable locations than would often be possible, were these organs 

 always obliged to arise directly upon a non-specialised mycelium at the 

 surface of the nutrient substratum (wood, bark, etc.). The well-known 

 ozonium of Coprinus domesticus functions in a similar manner to that of 

 Psathyrella disseminata. The occasional occurrence of fruit-bodies of 

 P. disseminata and of Merulius lacrymans on the surface of brick walls is 

 illustrated and explained. 



The author describes the structure of a fruit-body of Psathyrella 

 disseminata in detail. The spore-discharge period is about 18 hours in 

 length. The four generations of basidia have differential protuberancy 

 and are therefore tetramorphic. The longest set of basidia develops 

 spores first and discharges them first. The next longest set of basidia 

 develops spores next and discharges them next, and so on for the other 

 two sets 'of basidia. 



For the hair-like cells occurring on the surface of the top of the 

 pileus, the gill-sides, the gill-edge, and the stipe, the author has intro- 

 duced the terms pilocystidia, pleurocystidia, cheilocystidia, and caulo- 

 cystidia respectively. 



Quelet removed Psathyrella disseminata from the genus Psathyrella 

 in which Fries had placed it to Coprinus. There is no justification for 

 this change. A detailed study of the gills of P. disseminata shows that 

 these lack the distinguishing Coprinus characters, for (1) the spores do 

 not ripen on each gill from below upwards, (2) the spores are not dis- 

 charged on each gill from below upwards, and (3) autodigestion of the 

 gills from below upwards does not take place during spore-discharge. 



Chapter III.— In the Bolbitius Sub-type the fruit-body is ephemeral : 

 it opens, sheds its spores, and collapses within a period of about 24 hours. 

 The gills are not mottled. Whereas in the Psathyrella Sub-type the 

 basidia are (1) polymorphic, (2) crowded laterally so that there is over- 

 lapping of the spores, and (3) arranged in a definite series of generations 

 which are usually four in number, in the Bolbitius Sub-type the basidia 

 are (1) monomorphic, (2) not crowded laterally, and (3) not as a rule 

 arranged in definite sets or in strictly successive generations. In the 

 Bolbitius Sub-type, on any one small area of the hymenium, at any one 

 time, the basidia are usually in all stages of development but, occasion- 

 ally, they form four groups which can be recognised as four successive 

 basidial generations. The paraphyses are large and form a hymenial 

 pavement in which the basidia are set. 



