32 RESEARCHES ON FUNGI 



that of Hymenomycetes. The spores of gastromycetous fungi 

 are produced in closed chambers within the fruit-body instead 

 of on a free external hymenium. These chambers only open after 

 all the spores have ripened, so that the spores are unable to escape 

 one by one as they come to maturity. When the spores become 

 enveloped in a sweet fluid, as in the Phalloideae, the agent for 

 spore-dissemination is insects ; but, if the spores dry up and become 

 powdery, as in Lycoperdon, the agent is usually the wind. In no 



species of Gastromycetes do the 

 basidia discharge their spores 

 directly into the air. Now, in 

 the closed chambers of gastro- 

 mycetous fruit-bodies, violent 

 spore-discharge would not only 

 be useless but might be posi- 

 tively harmful. Assuming that 

 the Gastromycetes have been 

 derived from the Hymenomy- 

 cetes, it seems to me, therefore, 

 that violent spore-discharge has 

 become suppressed in the Gas- 

 tromycetes. Assuming such 

 suppression to have taken place, 

 we may suppose that the well- 

 developed sterigma, which, in association with the spore-hilum, 

 had the function of violently propelling the spore in the ancestral 

 Hymenomycetes, became useless during the development of internal 

 hymenial chambers and, therefore, in the course of the evolution of the 

 Gastromycetes, became either more or less suppressed or deformed. 

 This degeneration of a once useful structure finds parallels in the 

 reduction of the posterior pair of stamens in the flower of Salvia to 

 functionless staminodes, in the suppression of the eyes but not the 

 eye-stalks of certain American cave Crustacea, and in the almost 

 total obliteration of the hind limbs of the Python. 



The degeneration of the typical basidium in cleistocarpous 

 Basidiomycetes finds its parallel in the degeneration of the typical 

 ascus in subterranean Ascomycetes. In Discomycetes, e.g. Peziza, 



FIG. 12. Lycoperdon gemmatum, a 

 common Puff-ball. Basidia from the 

 hymenial chambers of a fruit-body. 

 The sterigmata are cylindrical in 

 form and variable in length, number, 

 and arrangement. The spores lack 

 hila and are not violently discharged. 

 After Ed. Fischer, from the Pflanzen- 

 familien. Highly magnified. 



