FRUIT-BODY FIXATION 127 



with the problem of fixation in nature consists of masses of irregularly- 

 piled dung-balls as dropped in pastures and other places by grazing 

 horses. 



The various external factors which play a part in the fixation of 

 a fruit-body are as follows : 



(1) Light which inhibits the development of the tiny rudiments 

 of fruit-bodies which may arise on the illuminated surfaces of the 

 substratum. 



(2) Light which inhibits the growth in length of the sohd stipe- 

 base as soon as the pileus has been pushed up into the fight. 



(3) Gravity which causes the stipes of young fruit-bodies to 

 push upwards through the substratum. 



(4) The structure of the dung-mass which consists of more or 

 less spherical or oval lumps of considerable size piled together so 

 that there are crevices between them. 



The internal factors which, independently of external stimufi, 

 play a part in the fixation of a fruit-body are as follows : 



(1) The continued development of a fruit-body rudiment in the 

 dark, if its growth is not inhibited by the growth of a more vigorous 

 neighbouring rudiment. 



(2) The early development of a long, sohd, stout stipe-base in 

 the dark, and the correlated delayed development of the combined 

 stipe-shaft and pileus beyond the size of a small cone. 



(3) The dense coat of free hyphae which grow outwards in all 

 directions from the exterior of the stipe-case and the lowest part 

 of the stipe-shaft. 



We shall now attempt to correlate the data which have been 

 brought forward in this and in the preceding Sections, and by this 

 means describe what may be termed the act of fixation of a fruit- 

 body. 



Tiny rudiments of fruit-bodies, not larger than about the size 

 of a pin's head, may and do arise simultaneously at many points 

 everywhere over the surface of the infected substratum, i.e. in the 

 Ught, in the dark, on upper or lower surfaces of the dung-balls or 

 in crevices between the dung balls. Of the scores or hundreds of 

 rudiments thus brought into existence only one or a few can possibly 

 survive, owing to the size of the fruit-bodies to be produced and 



