ii2 RESEARCHES ON FUNGI 



extraordinarily exact downward growth of the hymenial tubes. 

 Each tube grows downwards for 4-10 years and, according to Faull, 

 as we have seen, the portion of a tube produced in any one year 

 may function for as many as four successive years. If it were 

 not for the fact that each of the exceedingly narrow and relatively 

 very long hymenial tubes grows vertically downwards with mar- 

 vellous precision, it would not be possible for the spores shot from 

 the basidia to fall freely downwards in a tube's interior space ; 

 for the spores are adhesive, the air in each tube is perfectly still, 

 each spore falls vertically downwards often for an inch or more 

 within a tube, and, if a spore touches the side of a tube in its fall, 

 it sticks to it. The successful emergence of the spores through 

 the mouths of the hymenial tubes is strictly dependent on the axes 

 of the tubes being perfectly vertical. 



The Attachment of Fomes fomentarius Fruit-bodies. The 

 mycelium of Fomes fomentarius growing in a vertical Paper Birch 

 trunk (Betula alba var. papyri/era), when about to form a fruit- 

 body, bursts through the lenticels and cracks in the bark over 'an 

 area no larger than the print made by the tip of a finger or thumb 

 upon a sheet of polished glass (Fig. 39). The hyphae passing 

 through this area and thus connecting the mycelium in the wood 

 with the developing fruit-body thereafter conduct to the fruit- 

 body all the materials required for its growth in successive years. 

 As the fruit-body grows downwards by annual increments, it comes 

 to press against the trunk (Fig. 37) and, where it touches the corky 

 bark, it flattens out against it and becomes firmly adherent to 

 it without its hyphae penetrating through it. The result is that 

 it is not difficult to separate large Fomes fomentarius fruit-bodies 

 from Birch trunks by sudden pressure with the hand ; for, if one 

 presses such a fruit-body violently, the outer paper-like sheet of 

 cork (Birch bark) to which the fruit-body is adherent is loosened 

 from the inner sheets and, at the same time, the strands of hyphae 

 passing through the connecting area at the back of the top of 

 the fruit-body snap across. One cannot separate a fruit-body of 

 Fomes igniarius attached to an Oak tree in this way, for the bark 

 of the Oak does not consist of thin paper-like sheets of pure cork 

 but is mechanically very tough and resistant. 



