96 



THE OAK. 



as a thin sheet of closely-woven hyphae continuous over 

 the whole of the tip, and sending processes in between 

 the cells of the dermatogen, but not into the cavities of 

 the cells nor deeper into the tissues. Loose hyphse also 



Fio. 25. Longitudinal section of the tip of one of the roots marked ra in 

 Fig. 7, the outer layers of which are infested with fungus hyph^y 

 (mycorhiza); r.c, root-cap; ra, embryonic tissue from which all 

 originates ; P, pith ; p, spiral vessels of the primary xylem ; c, 

 cortex. 



radiate into the soil around, and often simulate the root- 

 hairs of other plants, which, in fact, they are said to 

 replace (Fig. 25,/). These hyphae are extremely fine 



