42 EESEAIKIIES ON FUNGI 



bodies, ('.(J. those of Myceiia e2npferygia, have ii distinct advantage 

 over thick-stiped, such as those of Russula emetica, in that, if the 

 fruit-body should be even considerably displaced by any accident, 

 it can quickly be set once more with the gills in vertical j)hines by 

 means of a suitable geotropic curvature of the stipe. With Kussuhe, 

 Psalliota?, &c., OAving to the thickness of the stipes, this is impossible 

 "when the pilei have become outstretched. In these cases, the gills 

 themselves react to the stimulus of gravity, and after a slight dis- 

 placement of the fruit-body, quickly readjust themselves so as to 

 come to lie in vertical planes once more ; but when the displacement 

 is considerable, this remedy becomes of very little avail. In species 

 of Galera, Mycena, &c., the structure of the stipe is such as to remind 

 one of the hollow peduncle which supports the capitulum of a 

 Dandelion or the pith-filled one of a Chrysanthemum. It is clear 

 that for the stipes of Agaricineie we have a series of variations 

 in the cylindrical form comparable with that found in the stems ot 

 Phanerogams and bearing a siujilar interpretation. 



A certain amount of rigidity is given to many stipes, not merely 

 by their cylindrical form, but also by longitudinal tensions set up 

 in the layers of hypha3 of which they are composed. The existence 

 of these tensions can easily be proved by })artial]y bisecting or 

 quadrisecting the stipes concerned, e.(j. those of Coprlnus comatus, 

 Mycenffi, &c., in a longitudinal direction from below upwards, with 

 a knife. The halves or quarters so produced bend outwards and 

 resist attempts to replace them in their original ])ositions (Fig. lo). 

 It is well known that similar tensions occur in the young stems 

 of the Higher Plants. 



The foregoing remarks tend to show that stipes in general are 

 well ada|)ted to give the basidia the lie.st })Ossible chance of dis- 

 charging their spores, so that they may freely escape from the 

 fruit-body. There can be no doubt that the pileiis flesh is adapted 

 to the same end. Its function is not merely to support the weight 

 of the gills or hymenial tubes, but to hold them tixed in one 

 particular position. As one might expect from a very simple 

 mechanical consideration, the ])ileus flesh is always thickest toward 

 the centre and thins out rapidly in the ])eripheral direction. Its 

 exact form and the materials of which it is composed vary much 



