FRUIT-BODY FIXATION 129 



always flow to the fruit-body which grows fastest, and feebler 

 rudiments have no power to divert the stream when once it has 

 begun to move quickly in one direction. The mycelium in a mass 

 of dung-balls just before fruit-body rudiments are formed upon it 

 consists of a single three-dimensional closely-knit network ; for 

 all the mycelia which have been produced from many separate 

 spores, or all the hyphae of a myceUum produced from a single 

 spore, have by this time become linked up through the formation 

 of vast numbers of bridging hyphae. A single developing favoured 

 rudiment, so far as the contents of this mycelial network is con- 

 cerned, has a definite sphere of influence which extends radially 

 for not more than a few inches. Within this sphere of influence 

 the rudiment extracts ultimately all the nutrient contents of the 

 hyphae, and with these it builds up its stipe-base, its stipe-shaft, 

 and its pileus. The final stage of activity of the emptying hyphae, 

 thus drawn upon, is probably the absorption of water for con- 

 duction to the stipe when this is undergoing its extremely rapid 

 elongation. When the mycehum is very extensive, there is room 

 for the development of several favoured rudiments at separate 

 points in the substratum ; and then each rudiment has its own 

 particular sphere of influence. In the end, under normal con- 

 ditions, the spheres of influence divide up the mycelium completely, 

 so that the whole of its contents are employed in fruit-body 

 production. 



A favoured rudiment which is able to continue its development 

 after the second and final selection process is, therefore, one which 

 has arisen at some little distance, an inch or so, below the upper illumi- 

 nated surface of the substratum, in a darkened crevice under a dung- 

 ball or between two or more dung-balls. Such a rudiment now 

 becomes differentiated into a solid stipe-base crowned with a 

 relatively tiny conical pileus enclosing the rudiment of the hollow 

 stipe-shaft. The developmental energy then becomes concentrated 

 upon the stipe-base. This swells and, as it grows in length, pushes 

 the tiny conical pileus away from the surface of the substratum 

 in the direction of least mechanical resistance. This is possible 

 owing to the fact that, at this stage of development, the rudiment is 

 ageo tropic and the stipe-base readily permits its form to be moulded 



VOL. IV. K 



