ADJUSTMENTS OF FRUIT-BODIES 67 



menon of geotropic swinging will be recorded in connection with 

 an account of Coprinus plicatiloides. 



The adjustments of a fruit-body of Coprinus plicatilis, by means 

 of which the successful liberation of the spores is secured, are three 

 in number: (1) The erection of the pileus by the bending of the 

 stipe ; (2) the raising of the pileus by elongation of the stipe ; and 

 (3) the adjustment of the gills by the expansion of the pileus. The 

 gills do not appear to be positively geotropic. Not only are they 

 small in size, but they split from above downwards in a manner 

 peculiar to many species of Coprinus. When the pileus expands, 

 they open out like the folds of a parasol. It is clear that the 

 hymenium is sufficiently adjusted to a suitable position by the 

 curvature of the stipe and the expansion of the pileus. A reaction 

 of the gills to gravity, like that which occurs in the Mushroom, 

 would be quite unnecessary. The relations of the fruit-bodies with 

 light were not investigated. 



For the Coprini generally, there appears to be an absence of 

 geotropic response in the gills. This peculiarity is correlated with a 

 very special mode of spore-liberation which will be described in 

 detail in Chapter XIX. 



Coprinus niveus. — This species is coprophilous, and is frequently 

 found in the autumn upon horse dung in fields. The fruit-bodies 

 which are snowy white, make their appearance at any place on the 

 free surface of the dung balls. At first they are strongly heliotropic 

 and with unilateral illumination simply grow toward the source of 

 light. This heliotropic response enables the stipes to push their 

 unexpanded and conical pilei outwards between, or from under, the 

 dung balls into the open. Growth toward the source of light con- 

 tinues until the stipe is some 3-4 cm. long. Shortly before the 

 pileus begins to expand, the top of the stipe ceases to be heliotropic 

 and becomes negatively geotropic : it makes a new curvature and 

 grows vertically upwards. This adjustment causes the whole pileus 

 with its gills to be placed in the requisite position for the successful 

 liberation of spores. Some horse dung obtained from a field was set 

 so that the fruit-bodies found growing upon it looked directly up- 

 wards. The oblique light from a window caused the stipes to make 

 a heliotropic curvature (Fig. 25, to the left). Afterwards, when the 



