82 THE AMERICAN MONTHLY [March 



own existence depends on the welfare of the alga. The 

 alga is not so completely overgrown as to keep out the 

 light, which would of course render it perfectly useless, 

 but is kept well lighted and is allowed to grow and mul- 

 tiply, so that the fungus too may increase in size. 



I have no doubt some of you will ridicule the idea of 

 calling this arrangement a partnership, especially as it 

 is known that many of the different forms of algsB which 

 are constituents of various lichens can perfectly well 

 lead an independent existence, and the advantage from 

 the protection of the fungus would therefore seem to be 

 a myth. Many might prefer to look upon the fungus as 

 a tyrannical employer of labor, crushing the independ- 

 ence of the working algsp, and binding them, not with 

 protective filaments, but with despotic chains. 



When reproductive cells are produced by such a fun- 

 gus they capture their working partners, or shall we 

 call them their slaves, by throwing out filaments, which 

 finally entirely enclose the algal cells. (Fig. 3.) This 

 is the beginning of the symbiosis, but once started the 

 fungus generally takes care that it shall continue. 

 Thus when the lichen gives off its vegetative spores it 

 practically surrounds a few algal cells with hyphse 

 and rounds the whole off into a spherical mass called a 

 soredium, the enormous quantities of which in some 

 lichens cover the growth with a powdery -looking sub- 

 stance. 



Let us now take another case of symbiosis between a 

 green plant and fungus. If you were to examine the 

 rootlets of almost any of our trees, such as the oak or 

 the beech, you would find them clothed in many places 

 with a mass of white or glistening hyphse, so thickly sur- 

 rounded in fact that the hyphae form a dense felt-work 

 completely covering the rootlets, which usually become 

 short and thick and tend to branch considerably. (Fig. 



