200 ROMANCE OF LOW LIFE AMONGST PLANTS. 



the large group of gill-bearing fungi — that is to say, 

 those of the mushroom type — we shall find that nearly 

 twenty-nine per cent, grow upon decayed wood. In 

 these cases, life having departed from the wood, the 

 mycelium penetrates the tissues, disintegrates the 

 cells, and produces a condition which we call decay, 

 but which is in effect reducing it to a pabulum 

 capable of supporting the life of the agaric which is 

 to be developed from the mycelium. Dead wood, 

 so long as it remains dry, resists the encroachments 

 of the fungus ; but when persistently moist it soon 

 falls a prey. All decaying wood is more or less pene- 

 trated by fungus mycelium, whether the fungus itself 

 is developed or not, the full development depending 

 upon a sufficiency of moisture or other surroundings. 

 Doubtless continued moisture predisposes the wood 

 to decay, dissolves what is soluble, softens the cell 

 walls, and induces a kind of fermentation ; the 

 grov/ing mycelium does the rest by slow disintegra- 

 tion, and the liberation of the chemical constituents, 

 so that the main factor in the destruction of dead 

 wood is fungus mycelium. Out of a total of 271 1 

 white-spored agarics no less than 924 are lignicolous. 

 Of 334 pink-spored species there are 81. In nearly 

 1000 brown-species, or dennini, 218 are found habitu- 

 ally on wood ; and of 608 blackish-spored agarics, 

 the melanosporcc, only 98 are lignicolous. Thus, in 

 4639 species of the Agaricini, 1321 are wood-loving 

 species, or, in fact, destroyers of wood. 



The destructive process is extended also in the 

 same manner to dead leaves fallen on the ground, 

 and consequently continually moist ; but their final 



