no RESEARCHES ON FUNGI 



narrowing the diameter of the tube, or whether the same hymenial 

 layer functions each year by the pushing up into it of new basidia 

 developed from the subhymenium. 



The Geotropism of Fomes fomentarius Fruit-bodies. There 



FIG. 38. Fomes Jomentarius. The fruit-body was attached at a to the under 

 side of a Birch branch and, reacting to the stimulus of gravity, grew conically 

 downwards in the air for five years. During this time it produced the five 

 successive annual hymenial tube-layers, 15. In the winter of the fifth year 

 the tree was over-turned, so that the fruit-body took up the position here 

 shown. The fruit-body then grew geotropically downwards at its edge, pro- 

 ducing in the sixth and seventh years the tube-layers 6 and 7 respectively. 

 From the shore of Indian Bay, Shoal Lake, Manitoba. Photographed by 

 C. W. Lowe. Natural size. 



can be no doubt that the stimulus of gravity plays a very important 

 role in moulding the forms of Fomes fruit-bodies and in determining 

 the direction of their growth. As an illustration of this fact, we 

 may consider the curiously-shaped fruit-body of Fomes fomentarius, 

 represented in Fig. 38, which was found by my colleague Mr. C. W. 

 Lowe on a fallen Birch tree at Indian Bay, Shoal Lake, Manitoba, 

 in July, 1921. The fruit-body had the orientation shown in the 



