THE GILL-CHAMBER 45 



copioides, one of the Thelephome, in which the hymenium is 

 smooth and not yet produced into tubes, teeth, or gills. The 

 length of the stipe in a few very tiny fruit-bodies is not 

 much more than a single centimetre, but in general it varies 

 from 5-12 cm. In different species it appears to bear some rela- 

 tionship to the size of the pileus and the usual nature of the 

 environment. In a single species the stipes of individual fruit- 

 bodies are often longest when development has taken place in 

 badly lighted places. The power of adjustment in response to 

 conditions of light doubtless finds its significance in the advantage 

 gained from raising up the pileus above surrounding obstacles. 

 In most species the stipe does not elongate when once the gills 

 have become outstretched, but in Coprinus comatus it goes on 



FlG. 15- — Lcpiota proccra. Section showing mode of attachment of the pileus 

 to the stipe. \ natural size. 



lengthening during the whole period of spore-discharge, so that 

 at the end it is often 30 cm. long. A good explanation can be 

 found for this exception to the general rule, but it will be more 

 conveniently dealt with in Chapter XIX., where the Coprinus type 

 of fruit-body is described in detail. 



In resupinate, dimidiate, and most fruit-bodies with centric 

 stipes, the gills are exposed from their earliest appearance. ' Guided 

 by this fact, we may regard the formation of a distinct gill-chamber, 

 such as occurs in the genus Amanita, Psalliota, &c. (Fig. 19), 

 as one of the later developments in the evolution of Agarics. 

 The significance of this structure is probably to be found in the 

 advantage derived from protecting the gills from insects, parasitic 

 fungi, and other enemies until the last possible moment, when 

 their expansion and free exposure to the air, for the purpose of 



