292 THE ROOT 



a push up and down the root. The region behind the 

 elongating region is held fast in the soil by the roqt 

 hairs, but the root apex, covered by the root cap, is 



Fig. 48. — Cross-section of a small root taken in the root-hair region : 

 r.h., root hairs; p. I., piliferous layer ; cor., cortex; e, endodermis; 

 per., -peticyci^; px., protoxylem; »;tr., metaxylem; ^A,. phloem (s.<., 

 sieve tube; c.c, companion cell). This root is diarch, i.e. with 

 2 xylem strands, joined to form a plate, and 2 phloem strands. 



pushed between the particles of soil, its passage being 

 lubricated by the mucilaginous surface of the cap. 



Internal Structure.^-A cross - section of the root 

 taken in the naiddle of the root-hair region gives the 

 best idea of the primary plan of construction of the 

 root. On the surface is the piliferous layer (Fig. 48,^. Z.), 



