378 RESEARCHES ON FUNGI 



A flattening of the pileus, with a consequent raising of the 

 gills, occurs toward the end of pileus expansion not only in the 

 Common Mushroom, but in many other large Agaricineae. For 

 Amanita rubescens it is shown photographically in Figs. 135 

 and 136. 



The Radial Arrangement of the Gills. Granted that the 



FIG. 135. Amanita rubescens. A fruit-body with a convex, still ex- 

 panding pileus. The annulus, which formed the base of the gill- 

 chamber, is now hanging downwards and hence is not an obstacle to 

 the falling spores. Photographed at Four Oaks, Warwickshire, by 

 J. E. Titley. About natural size. The pileus was 4 inches in 

 diameter. 



lamellae are useful to the fruit-body in that they serve to increase 

 the amount of surface available for the hymenium, yet we may 

 still ask why they should be arranged in a radial manner. Why 

 should the gills stretch along radii from the stipe to the periphery 

 of the pileus and never form concentric bands ? I believe that the 

 answer is as follows : (1) the radial arrangement involves a less 

 complicated adjustment in securing that the lamellae shall look 

 directly toward the earth than would the concentric one, and 

 (2) the radial arrangement, with its radial interlamellar spaces, 



