FUNGI IN GENERAL 109 



the support of a new generation, and leaving behind some of 

 the results of disintegration to assimilate with the soil. The 

 gardener makes, in a useless corner, his pile of the castaway 

 twigs and cuttings of his trees and the derelict haulms of herbs 

 and vegetables". Soon, over the whole putrescent surface, 

 mycelium and mould proclaim the advent of a new era of 

 vegetable activity, and anon the whole mass teems with new 

 life. In this metamorphosis as the Fungi flourish the twigs 

 decay, for the new life is supported at the expense of the old, 

 until finally both destroyers and destroyed return again to the 

 soil from whence they were derived, to form fresh pabulum for 

 a succeeding season of green leaves and sweet flowers. What 

 we call decay is mere change — change of form, change of rela- 

 tionship, change of composition ; and all these changes are 

 effected by various combined agencies — water, light, air, heat, 

 these furnishing new and suitable conditions for the develop- 

 ment of a new race of vegetables. But what a potent agent 

 have all these in the myriad forms of Fungi, which, above and 

 beyond all other conditions of vegetable life, deserve the name 

 of the " Great Destroyer." 



We have already intimated that the relationship of Fungi 

 to Lichens is closer than to any other of the Thallophytes, as 

 evidenced by their association, in some methods of classifica- 

 tion, as members of a mycetal alliance. It may be useful to 

 indicate here some of the general features in which Lichens 

 differ from Fungi, in addition to those set forth in the short 

 diagnosis. 



Lichens are perennial ; they grow very slowly, but they 

 attain an extreme age. Some species, grown on the primitive 

 rocks of the highest mountain ranges in the world, are esti- 

 mated to have attained an age of at least a thousand years ; 

 and one author mentions, after the lapse of nearly half a 

 century, having observed the same specimen of Sticta pulmon- 

 aria on the same spot of the same tree. On the other hand, 

 the Discomycetous Fungi, which are closest in alliance, are 

 annual, very short-lived, their whole existence being limited 

 to a few weeks, rapid in growth and rapid in decay, not a 

 trace of some species remaining after a few days. 



Lichens will exist under conditions of aridity which no 



