204 



BOTANY AND PHARMACOGNOSY. 



The root branches arise as the product of a meristem, 

 known as the pericambium, situated beneath the endodermis 

 (Figs. 59. RB ; 109). The tissues forming the branches are 

 directly connected with the fibrovascular tissues of the root and 

 protrude through the overlying tissues without having any con- 

 nection with them. The structure of the branches thus formed 



Fig. 1 13a. Longitudinal section through a root of Veralruin viride showing the nature 

 of the contraction of the root; E, epidermis; OS, cells of cortex containing starch; CO, 

 cells of cortex containing raphides; F. fibrovascular bundle; A, rifts or cavities formed as 

 a result of the radial swelling of the cells of the cortex. 



corresponds to the primar\' structure of the roots, and in the case 

 of dicotyledonous roots may also subsequently develop a secondary 

 structure. Goebel states that in plants which grow in moist 

 soil, or whose roots function only for a short time, the branches 

 may be altogether suppressed as in Colchicum, Arissema, etc. 

 Contraction of roots is observed in both monocotyledons 

 and dicotyledons, it being most apparent in the former, as in the 



