Environment and Adaptation 213 



beech, and many species growing in humus, such as 

 some of the Heath family, e.g., species of rhododen- 

 dron and huckleberries. In such saprophytes as the 

 Indian-pipe (Monotropa), and the coral-root or- 

 chids, which are without chlorophyll, the fungi fur- 

 nish not only nitrogen, but also carbon in some form. 

 It seems likely that the carbonaceous matter from 

 the humus is first elaborated by the fungus, which is 

 then itself destroyed within the tissues of the host. 

 There seems to be a sort of mutual parasitism. The 

 fungus at first feeds upon the host, which after- 

 wards retaliates, and destroys the fungus within its 

 tissues. 



The most familiar case of symbiosis is that of the 

 lichens, where a fungus and an alga are intimately 

 associated. While in this association the fungus un- 

 doubtedly behaves as a true parasite toward the alga, 

 which under favorable conditions can grow quite 

 independently, there seems no reason to doubt that 

 the alga itself derives some benefit from its associa- 

 tion with the fungus. Within the sheltering tangle 

 of fungus filaments it is supplied with water, and it 

 is quite probable that a certain amount of nourish- 

 ment, presumably of a nitrogenous nature, is also 

 supplied to it. 



Synchytrium papillatum. That many parasitic 

 fungi are of comparatively recent origin is certain, 

 as some species may be associated with a specific 

 host, which is often a highly organized and pre- 

 sumably a recent type of flowering plant, and the 



