ADJUSTMENTS OF FRUIT-BODIES 77 



and probably also in certain others where the fruit-bodies are 

 diminutive., there is only one response to gravity, namely, that 

 of the stipe. This is sufficient to place the tiny pilei so accurately 

 in the erect position that the gills look downwards and successful 

 spore-liberation can take place. In larger ground Agaricinese with 

 deep gills, e.g. the Mushroom, an extra response is requisite, 

 namely, that of the gills themselves. The most complex of all 

 Agaricinere in relation to gravity, doubtless, are certain large 

 species, such as Pleurotus ostreatus (Figs. 2 and 3, pp. 22 and 23), 

 which grow on trees and stumps. These probably have four geo- 

 tropic reactions similar to those already discussed for Polyporus 

 squamo8us; (1) Negative geotropism of the stipe; (2) diageotropism 

 of the pileus flesh; (3) eccentricity of development; and (4) 

 positive geotropism of the gills. 



It is the rule with Hymenomycetes that the mycelium gives 

 rise to a great many more rudimentary fruit-bodies than can 

 possibly come to maturity. On a Mushroom bed one may often 

 observe some hundreds of such rudiments within the space of a 

 few square inches ; and even in Polyporus squamosus the rudi- 

 ments are generally at least twice as numerous as the mature 

 fruit-bodies (Plate V., Fig. 31-34). It generally happens that a 

 very limited number of the rudimentary fruit-bodies obtain the 

 advantage over their fellows and commence to grow rapidly. The 

 food supply is thus drawn to them, and the unsuccessful rudi- 

 ments at once cease their development and become aborted. The 

 production of a great many rudiments at the beginning of repro- 

 duction increases the chance that some of them will be suitably 

 situated for successful development. In some species, it generally 

 happens that a number of rudiments continue their development 

 ;ide by side, so that at maturity the fruit-bodies are more or less 

 crowded. The crowding in Collybia velutipes, Coprinus micaceus, 

 and Armillaria meUea (Fig. 30), &c., may become so excessive 

 that a large proportion of the spores produced are prevented from 

 escaping from the fruit-bodies. Such overcrowding seems to be 

 a distinct imperfection in fungus development. 



We may summarise the general conclusion from the observa- 

 tions recorded in this chapter as follows. The fruit-bodies of the 



