36 



RESEARCHES ON FUNGI 



and yet never be less than a certain minimum Avidtb, are seen 

 in the Oyster Fungus (Pleurotus ostreatus, Figs. 2 and 3) and 

 in the Mushroom (Fig. and Plate IV., Fig. 25). Certain species 

 of Russula have gills which arc all of one length, Avith the 

 exception of very occasional shorter ones (Fig. 10). Since the 

 gills in the fully-expanded fruit-bodies diverge considerably in 



Fig. 9. — Psalliota cavijjoitris. Part of 

 ii pilous photographed from below, 

 showing that the gills are accu- 

 rately a(ljuste<l so that they look 

 directly downwards. Natural size. 



Fig. 10. — The pileus of Ruxsula nigricans — 

 an Agaric in which the gills are very 

 coarsely spaced. The stipe is maggot- 

 eaten. Reduced to \ natural size. 



passing from the stipe to the margin of the pileus, their arrange- 

 ment appears to be relatively imperfect. 



The principles underlying the arrangement of the gills of the 

 Agaricineie doubtless also apply to the arrangement of the hymenial 

 tubes beneath the pilei of species of Polyporeie. Other things 

 being equal, the greatest economy is effected when the tubes are 



