502 



BOTANY AND PHARMACOGNOSY. 



4^-~ 



Fig. 2 20. Pinkroot {Spigelia marilandica): A, transverse section of root showing 

 epidermis (e), parenchyma containing starch (p), peripheral layer of central cylinder (1), 

 endodermis (e), internal layer of cortex (i). The central cylinder consists of six to eight 

 radial fibrovascular bundles, and some of the tracheae contain a brown gummy substance. 

 B, transverse section of rhizome showing epidermis (t), the outer wall of which contains a 

 yellowish-brown substance, parenchyma (p) of cortex containing starch, sieve of cortex 

 (s), cambium (c), tracheae (t), tracheae (r) containing globular or somewhat irregular 

 yellowish-brown masses, tracheids (h), internal sieve groups (s), parenchyma of pith (p') 

 containing starch. C, longitudinal section of the woody part of the rhizome; D, isolated 

 starch grains, which are 2 to s n in diameter. 



