SAPROPHYTISM AND SYMBIOSIS 337 
evidence of the parasitism of some fungus on the tree. 
Several species of fleshy fungi are, in this way, parasitic 
or partly parasitic. In ectotrophic infection the hyphae 
penetrate through the epidermis and then grow and branch 
underneath it, some of the branches growing between the 
individual epidermal cells by dissolving the middle lamella 
with enzymes which they secrete. In this manner there 
is formed a pseudo-tissue, closely analogous to a lichen, 
which replaces the true epidermis. The fungus doubtless 
derives some nourishment from the dissolved (digested) 
FIG. 245. Tangential section of root of the red maple (Acer rubrum), 
showing endotrophic micorhiza in the cells. (After W. B. McDougall.) 
substance of the middle lamella, as well as from nutrient 
substances that diffuse out from adjacent cells; but there 
is no evidence that the tree is in any way benefited by the 
presence of the fungus. 
In some cases the development of the mycorrhiza- 
mantle inhibits the growth of the root, and stimulates a 
profuse branching, which is repeated as the branches are 
infected. This gives rise to a malformation known as 
"coral root," which is so well developed in one herbaceous 
species as to give the plant its scientific as well as its 
common name Corallorhiza, or coral-root. 
In endotrophic mycorrhizas the hyphae penetrate 
through the cell-walls into the cell-cavities, and in such 
