90 POWDERED VEGETABLE DRUGS 



Glandular parenchyma cells as of rhizomes, barks, pericarp, seed tis- 

 sue, etc., are very frequently of great diagnostic value. 



5. Bast. This is very important. Carefully note the length 

 and diameter of cells and whether they occur singly or in groups. 

 Note porosity and thickness of cell walls. In some instances (cin- 

 chona, cinnamons and others) the bast cells are short and thick, ap- 

 proaching the character of sclerenchyma. Again, the cells may be 

 branching, as in Prunus and Viburnum. Contents of bast cells are 

 rarely diagnostic. 



6. Crystal-Bearing Fibers. These accompany the bast fibers. 

 They consist of rectangular, thin-walled cells united end to end, each 

 cell bearing a prismatic crystal of calcium oxalate. Their function 

 is in all probability mechanical, giving additional support to the bast 

 fibers. These fibers may prove of great diagnostic value, as in Que- 

 bracho. 



7. Sclerenchyma. Sclerenchyma cells are even more diagnostic 

 than bast. They vary in form, size and thickness of walls. They 

 may occur singly or in groups. They are mostly typical that is, 

 approximately isodiametric, thick-walled and porous. Again, they 

 may be rectangular, elongated or branching. Rarely is the color and 

 lamellation (Goto) characteristic. In some instances (cinnamon) the 

 walls are not uniformly thickened. Contents of sclerenchyma cells 

 are rarely diagnostic. Note number, size and branching of pores. 



8. Medullary Rays. This tissue is very prominent in some barks. 

 Note number of cell rows and size of cells, porosity of walls; and cell- 

 contents, as starch, resin, crystals. 



9. Epidermal Tissue. This is, of course, wholly wanting in the 

 older barks, having been displaced and pushed off by the deeper tissue. 

 The same may be said of the chlorophyll-bearing parenchyma which 

 in the younger branches occurs beneath the epidermis. 



5. ROOTS AND RHIZOMES 



Roots and rhizomes are closely similar in histological structure. 

 In the powdered state there is no reliable means of distinguishing 

 between them, either microscopically or macroscopically. The 'color 

 of the powder is rather variable. The predominating color is light 

 brown, often tinged with ash-gray, but there are exceptions, as the 

 deep reddish-brown of rhatany and the yellow of licorice, hydrastis 

 and curcuma. Some are very light, as Irisflorentina, Colchicum corm 

 and Althaea. Any of the typical tissues may be present, excepting 

 epidermal tissues and trichomes, which are very sparingly present if at 

 all. 



