ADJUSTMENTS OF FRUIT-BODIES 



6i 



The shape of the pileiis seems to be partly decided by the 

 direction of the conical process upon which it develops. When 

 a conical process happens to point vertically upwards (as it very 

 rarely does), the stipe to which it gives rise is vertical and the 



Fig. 22. — Polyporus squumosus. Under surface of a large fruit-body with a central 



stipe. J natural size. 



pileus horizontal from the moment of their differentiation {ef. 

 Plate v., Fig. 35). Under these circumstances, since the internal 

 developmental forces are symmetrically disposed, the pileus simply 

 grows at an equal rate all round its periphery. In response to 

 a diageotropic stimulus, it spreads itself out in a horizontal plane. 



