FRUIT-BODY FIXATION 131 



base is immersed in the substratum are of a mechanical nature, and 

 shortly they will be considered in detail. There would be no special 

 advantage in the solid stipe-base being continued upwards into the 

 air above the surface of the substratum ; and the inhibitory action 

 of the hght on the growth of the stipe-base always prevents pro- 

 jecting stipe-bases from coming into existence. In this matter the 

 sun's light is a beautiful regulator. 



With the emergence of the pileus into the light and the inhibition 

 of the growth in length of the soUd stipe-base, the growth-energy of 

 the fruit-body becomes concentrated upon the development of the 

 small conical pileus, which now quickly assumes a barrel-shaped 

 form and becomes many times larger. After a few days, the barrel- 

 shaped pileus attains its full growth in size and the spores begin 

 to develop at the surface of the gills. The stipe-shaft, which is 

 hollow, then grows rapidly in length and raises the pileus to a height 

 of from 6 to 10 inches from the ground. If for any reason, when 

 the stipe-shaft is growing upwards in response to the directing 

 stimulus of gravity, one side of the fruit-body is darkened owing 

 to the existence there of some dark object, the stipe becomes inclined 

 away from the object toward the source of greatest illumination 

 and may thus become deflected from the vertical by an angle of 

 about 10°. The pileus, whilst still being raised to its final altitude 

 in space, expands umbrella-wise. As soon as it has become cam- 

 panulate, the process of autodigestion sets in and the spores begin 

 to be discharged. Finally, the pileus becomes flattened so as to 

 form a disc with more or less re volute edges. The gills and the 

 peripheral portions of the pileus are gradually destroyed by auto- 

 digestion and, by the end of the spore-discharge period which con- 

 tinues for about 8 hours, the pileus has become reduced to a mere 

 tattered stump. A few hours after spore-discharge has ceased, the 

 shaft of the stipe loses its vitahty and collapses. The most persistent 

 part of the whole fruit-body is that which comes into existence first, 

 namely, the stipe-base ; but this, too, dies a few hours after the 

 collapse of the stipe-shaft. 



In consequence of the fruit-body developing in the manner 

 which has just been described, the full-grown stipe is found to 

 consist of two distinct parts which are differently constructed and 



