Kelley 



120- 



Mycotrophy 



an environment they are apt to be crumpled, shortened and otherwise 

 indicative of an untoward environment. These considerations again 

 show the casual nature of the mycorrhizal relationship. 



The Mycorrhizal Apex: — The effect of habitat on rootlet is 

 perhaps never better shown than in the root-cap region. In aquatic 

 roots where there is little resistance to apical growth, the apex may be 

 freely exposed ; or, if there is a root-cap as in Eichhornia, it grows to 



"'^'^:^-^!: 



■■^•':-r--ii,-n;<tii 



Fig. 7. — Longitudinal section through apex of a mycorrhiza of Pinus 

 rigida. r.c., root-cap; me, meristem; m, mantle; h, Hartig net; e, endo- 

 dermis, filled with "tannin". 



a relatively enormous size and fits loosely over the apex. Aesculiis, 

 grown in water culture, produces roots that "keine Wurzelhaube haben 

 und diese ihnen von ihrer ersten Entwicklung an fehlt". (Klein & 

 SzABO, 1880). In ordinary root-hair roots (as in Zea), there is a 

 close-fitting root-cap formed from a definite zone of proliferation in 

 the proximal portion of the apical meristem. Pressure of rootlet 



