CHAPTER IX. 

 SYMBIOSIS. 



55 \5. NUTEICISM. 

 Km; the "Teater number of the facts used in our discussion 



O 



<>f this peculiar phenomenon, we are indebted to Frank, who 

 laid the basis of uur knowledge in regard to it. We have 

 chosen the expression Nutricism for reasons already stated 

 (3 14), and would only add that its scope is variable in different 

 cases, and reaches its most comprehensive application in connec- 

 tion with Frank's views on the so-called mycorhiza. We shall 

 best explain the phenomenon by describing individual examples. 



In a number of cases the symbiosis between fungi and higher 

 plants does not result in the fungus being supplied with organic 

 nutriment by its host, but rather that the fungus is in no way 

 indebted to the host-plant for nutriment, and may even, as in the 

 lichens, convey solutions of inorganic materials to it, thus assist- 

 ing in its nutrition. There are two cases distinguishable in this 

 connection. In the first, the fungus lives in humus and in 

 close external contact witli the roots of its host, obtaining 

 food for itself, and at the same time supplying its host 

 with organic nutriment. In the other case, the fungus develops 

 inside the root-cells of its host, and is probably nourished from 

 that source, till on dying it gives up certain albuminoid sub- 

 stances, which are absorbed and utilized by the host-plant. The 

 parts of the roots which shelter the fungi, Frank has named 

 " fungus-traps," the plants themselves being " fungus-digesting 

 plants." 



The organs resulting from the symbiosis of root and fungus 



