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PHARMACEUTICAL BOTANY 



2. Hypodermis. 



3. Primary cortex with usually small intercellular spaces. 



4. Endodermis, or innermost layer of cells of the cortex* with 

 lenticularly thickened radial walls. 



f , 5. Pericambium of one to two layers 



of actively growing cells which may 

 produce side rootlets. 



6. Radial fibro-vascular bundle of 

 four, rarely two or three or five or six 

 phloem patches alternating with as 

 many xylem arms. Not uncommon to 

 find bast or phloem fiber along outer 

 face of each phltfem patch. Xylem 

 has spiral tracheae, internal to these a 

 few pitted vessels, then, as root ages, 

 more pitted vessels, also xylem cells 

 and wood fibers make their appearance. 



7. Pith, a small zone of parenchyma 

 cells. 



B. Of Secondary Growth (Most official 

 roots). 



At about six weeks one notes cells 

 dividing by tangential walls in the inner 

 curve of phloem patches. This is in- 

 trafascicular cambium. A single layer 

 of flattened cells starts to cut off on 



elusive; g, primary xylem bun- its inner side a quantity of secondary 



xylem and pushes out the patches of 

 bast fibers, adds a little secondary 

 phloem on the outer side. Secondary 

 xylem finally fills up the patches between 

 the arms. The patches of bast fibers get flattened out. The 

 pericambium has a tendency to start division into an inner and 

 outer layer. The outer layer becomes a cork cambium (phellogen) 

 surrounding the bundle inside of the endodermis. It cuts off cork 

 tissue on its outer face, hence all liquid material is prevented from 

 filtering through and cortex including endodermis, as well as the 



d ; Vc r -L e S 

 portion of root: lettered as in A; 



* C0rk " 



