04 



THE OAK 



forming an almost continuous ring (fig. 24, se.pli), and 

 consisting chiefly of the sieve-tubes and cells developed 

 from the cambium cylinder, the small primary phloem 



pr.K 



a. 24. Transverse sections (semi-diagrammatic') of roots 

 of oak, to be compared with fig. 7. The smaller figure, 

 above, shows the cambium ring, cam, now developed as 

 a continuous layer running inside the primary phloem, 

 pr.ph, and outside the primary xylem, pr.x ; and the 

 larger figure shows the results of its activity in the 

 formation of secondary phloem, se^k, inside the primary, 

 and secondary xylem, se.x, between the primary xylem 

 groups. In both cases, ep, piliferous layer; c, cortex; 

 P, pith ; sh, endodermis. Within the latter lies the 

 pericycle, in which the cork cambium, c.cam, is now 

 developed. 



