PSALLIOTA CAMPESTRIS 



455 



shot its spores from its basidia into the interlamellar spaces, the 

 production and liberation of the spores thus continuing for a spore- 

 fall period occupying several days. In this ancestor, in the course 

 of evolution, we must suppose that a series of changes took place 

 which profoundly altered the mode of spore-liberation and rendered 

 the beautiful gunnery of the basidia super- 

 fluous and useless. Owing, possibly, to one 

 or more mutations : (1) the gills became 

 branched and anastomosing ; (2) the 

 pileus ceased to expand in the usual way 

 at maturity ; (3) the spores ceased to be 

 shot away from their basidia and, on 

 ripening, merely accumulated in the gill- 

 folds and cavities ; (4) the pileus-flesh 

 became tougher and more resistant to 

 decav ; and (5) the liberation of the spores 

 imprisoned in the gill-folds and cavities 

 came to be effected by the gills drying 

 and becoming friable and by the dry 

 spore-powder falling through cracks in 

 the unexpanded pileus. Thus, to a certain 

 extent, the fungus came to resemble a Puff- 

 ball in both its outward form and its mode 

 of evacuating its spores. However, whilst a 



Puff-ball, e.g. Lycoperdon gemmatum or L. giganteum, gives one the 

 impression of having a structure which is beautifully adapted to 

 secure the liberation of the spores, 1 one does not gain a similar 

 impression on beholding the irregularly cracking, often misshapen 

 fruit-bodies of Secotium agaricoides. These fruit-bodies rather look 

 like monstrosities, indeed, as if they had recently changed their 

 mode of spore -liberation but were still structurally imperfectly 

 adapted to the new functional demands made upon them. 



1 Cf. these Re-searclies, vol. i. 1909, p. 258. 



157. Pholiota erebia. 

 An abnormal fruit-body : 

 the gills, instead of being 

 simple, exhibit irregular 

 branching and anasto- 

 mosis. Photographed 

 at Scarborough, Eng- 

 land, by A. E. Peck. 

 Natural size. 



