TIIK M VI i:KI AL OUT(H) OF PLANTS 



343 



connected >eries, extending from the tool hair region t<> the mesophyU of 

 the leaves, among which they branch so extensively thai there is s< an ely 

 a cell which is separated from a strand by more than a half dozen of 

 its neighbors. 

 Here the first 

 branches end 

 blindly (fig. 

 638) or join 

 their fellows. A 

 section of the 

 root in the root- 

 hair region 

 shows likewise 

 that only a few 

 cells intervene 



between the free surface and the young xylem strands, which, nearer 

 the root tip, are being differentiated from the plerome (p. 239). Like- 



Fig. 638. —Ending of a xylem strand among the cells of the 



mesophyU in a leaf of lilac (Syringa vulgaris) : I, trachcid ; i, in- 

 tercellular space. 



Fig. 630. — Skeletonized cdpe of a leaf of a Finis, shoving the mode of branching of 

 the smaller ribs ; the smallest are completely gone. — From a photograph by Land. 



wise, a section of the leaf (fig. 627, p. 319) shows the relations of this 

 water-conducting tissue to the surface, and an examination of the vena- 

 tion of various leaves (of which only the larger veins are visible to the 



