Late Mee ee et ae ere 
1 68 PHARMACEUTICAL BOTANY 
patches alternating with as many primary xylem (protoxylem) 
arms. It is not uncommon to find bast fibers along the outer 
face of each phloem patch. Xylem has spiral trachez, internal 
Cork Cambium : = PP ie 
1 3 -E-ndodermis 
‘ 
Root Hair 
Root Cap—-- 
Fic. 101.—Diagram of a longitudinal section of a root, showing secondary 
thickening and the disappearance of the primary cortex. Endodermis then 
becomes surface layer beneath which is formed the cork by the pericycle. p', p”, p*, 
phloem formed during first, second and third years; xy!, xy’, xy°, xylem formed dur- 
ing first, second and third years. (Mottier.) 
to these a few pitted vessels, then, as the root ages, more pitted 
vessels, also xylem cells and wood fibers make their appearance. 
6. Pith (from plerome), a small zone of parenchyma cells 
(not present in all dicotyl roots of primary growth). 
ON GS > oe te Se ee Se ees Sees seed 
