190 RESEARCHES ON FUNGI 



of development of the hymenium ; and it also clearly demonstrates 

 that the laminae owe their dorsiventrality their sterility on their 

 upper surfaces and their fertility on their lower surfaces to the 

 stimulus of gravity. 



It is quite possible that Sparassis, although now developing 

 like a compound Stereum, was originally derived from a Clavaria, 

 for it arises from the ground on a central stem, branches and re- 

 branches like many branched Clavariae, and has soft Clavaria-like 

 flesh. We have only to suppose that the original erect, radial, 



FIG. 67. Sparassis crispa. Position of the hymenium. A, one of the terminal 

 fronds of a large fruit-body showing its naturally curled condition. B, C, 

 and D, vertical sections through parts of a fruit-body. The blacker lower 

 lines, h h, represent the hymenium which always looks downwards. B 

 shows anastomoses of fronds. D is an S-shaped frond with the hymenium 

 on the lower side of each ascending part. Natural size. 



fertile branches, covered with cylindrical layers of hymenium, 

 became drooping, flattened, and at the same time responsive to a 

 morphogenic stimulus of gravity, which caused them to become 

 dorsiventral with a barren upper side and a fertile under side. 

 The general habit and the nature of the flesh therefore suggest 

 that Sparassis may have become thelephoraceous rather by con- 

 vergence than by direct descent. The view that such an approach 

 to the Thelephoreae may have taken place in the course of 

 evolution is supported also by the fact that in certain species of 

 Pterula, to which reference has already been made above, the 

 branches have become slightly compressed and also dorsiventral, 

 the hymenium being restricted as in true Thelephoreae to the 

 ventral surface only. 



The Genus Calocera. This genus, in accordance with the 



