CHAPTER V 



AN ANALYSIS OF THE FACTORS CONCERNED IN THE MECHAN- 

 ICAL FIXATION OF THE FRUIT-BODY OF COPRINUS 

 STERQUILINUS IN ITS SUBSTRATUM 



Introduction — Fruit-body Fixation in certain Polyporaceae and Agaricineae — 

 Coprinus sterquilinus — The Mycelium at the Surface of the Substratum — The 

 Mycelial Strands within the Substratum — The Rudiments of Fruit-bodies — 

 Light inhibits the Growth of Rudimentary Fruit-bodies — The Morphogenic 

 Effect of Light on Developing Fruit-bodies — The Relations of the Fruit-body 

 with Gravity — The Upward Pressure of the Stipe — The Heliotropic Effect of 

 Light — The Mechanical Fixation of the Fruit-body — Conclusion 



Introduction. — The hymenomycetous fruit-body, as we have seen, 

 functions successfully as an organ for the production and liberation 

 of spores only when it is formed in the air and is there held in one 

 fixed position. Therefore the ways and means by which Hymenomy- 

 cetes solve the problem of mechanical fixation for their fruit-bodies 

 is well worth enquiry. The factors which enter into fixation are 

 not always the same but may differ in different species ; and, as 

 evidence thereof, a brief description of the mode of fixation of the 

 fruit-bodies of a few of the larger Polyporaceae and Agaricineae 

 will be given in the next Section. The rest of the Chapter will be 

 devoted to a full discussion of the various factors which enter into 

 the fixation of the fruit-bodies of a large coprophilous fungus, 

 namely, Coprinus sterquilinus. 



Fruit-body Fixation in certain Polyporaceae and Agaricineae. 

 — Fomes fomentarius has large hoof-like fruit-bodies which, in 

 Canada, are often seen on the standing trunks of the Paper Birch 

 (Vol. II, Figs. 36 and 37, pp. 106 and 109). Each fruit-body is 

 attached to a tree-trunk by its whole surface of contact, as may be 

 seen by a study of the back of the fruit-body shown in Fig. 53 

 (also cf. Volume II, Fig. 39, p. 113). The fixation of a large, several- 



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