MICROSCOPICAL EXAMINATION OF POWDERED VEGETABLE DRUGS 91 



1. Epidermal Elements. 'These are usually indistinct or wanting; 

 when present compare with those of the leaf and stems, which see. 

 Trichome are quite universally absent. Terminal rootlets are quite 

 generally lost in collecting; hence, hair-cells are not found. Epidermal 

 cells, when present, do not present any special diagnostic features; 

 they are usually suberized. 



2. Cork. Suberized tissue is quite generally present and displaces 

 the epidermal tissue. As a rule, it presents no strikingly diagnostic 

 features in the form and number of cells, or in cell-contents. The 

 cell-walls are quite uniform in thickness and coloration. 



3. Parenchyma. 'This tissue is, as a rule, quite typical and abund- 

 ant. The cells do not vary greatly in size and thickness of walls. 

 In monocotyledonous roots and rhizomes they are, as a rule, consider- 

 ably elongated in the long ax's of growth. The peripheral cells are 

 tan gentially flattened and smaller than the more centrally located cells. 



The cell-contents are highly important and diagnostic; above all 

 the starch granules. It must, however, be kept clearly in mind that 

 the pasty starch of certain drugs, as sarsaparilla, curcuma and others, 

 is not a natural product, but artificially producd by heat. Such 

 starch usually occurs in lumps of the dimensions of the cell-lumen 

 (Curcuma), the individual granules having lost their structural char- 

 acteristics almost entirely. 



Unmodified granules should be critically studied and compared as 

 to size, form, position and size of hilum, distinctness of lamellation, 

 etc. Are they simple or compound? Are the granules free or do they 

 form aggregates? If compound, do the granules occur in twos, threes 

 or fours? The careful study of starch granules cannot be too strongly 

 emphasized, as it will not only be the key to the identification of the 

 powders, but will also be of inestimable value in the recognition of 

 starchy or starch bearing substances which are quite frequently 

 employed as adulterants. 



Parenchyma cells frequently contain crystals, usually of calcium 

 oxalate. These may occur as fine granules (belladonna), prismatic, 

 aggregate and acicular crystals. The aggregate and acicular forms 

 vary most in size. The form and size of the crystals is of great diag- 

 nostic value. 



Resin and mucilage bearing cells are often diagnostic. Note the 

 size of the resin-bearing cells and the color of the resin. Wax-like 

 and other cell-contents may occasionally prove diagnostic. 



Inulin is very abundant in certain plants taking the place of starch, 

 and will, therefore, prove very diagnostic in comparison with starch- 

 bearing plants. 



