340 
ILL miRAUONS. 
Plate VIII. 
CHANGE FROM PRIMARY .TO SECONDARY STRUCTURE 
IN THE ROOT. 
Fig. 60. — Transverse section of root of pea about 40 mm. from 
the root-cap: (H), epidermal cells, some of which are 
developed to root hairs; (C), primary cortex; (EN), 
endodermis; (X), xylem ; (P), phloem; the arrange- 
ment of sieve and ducts forming radial fibrovascular 
bundles. 
Fig. 61.— -Section in the older pait, higher up on the root show- 
ing in addition to what has been observed in Fig. 60, 
the beginning of the change from primary to secondary 
structure : (CA), the development of a cambium ; (SX), 
secondary xylem, and (SP), secondary phloem. 
