86 ... POWDERED VEGETABLE DRUGS 



9. Spongy Tissue. The cells of this tissue are also delicate and 

 readily crushed. They vary in form and size. Frequently they con- 

 tain chlorophyll and aggregate and prismatic crystals of calcium 

 oxalate. They may contain coloring matter, resin and wax. 



10. Stone-Cells. Typical or well-defined sclerenchyma cells in the 

 leaf parenchyma are rare, but very characteristic when present, as, 

 for example, the large branching stone-cells of tea and hamamelis. 

 There are other mechanical elements associated with the leaf blade, 

 but they are rarely of any diagnostic value in powders. Among these 

 may be mentioned the mechanical pillars in eriodictyon, the lateral 

 lines or ridges of coca, and the mechanical cells of the olive leaf, etc. 



11. Vascular Tissue. This is abundant in all leaves, but presents 

 no diagnostic features. It consists of ducts (porous reticulate, spiral 

 and annular), bast and tracheids. 



12. Glands. Though common and often containing important 

 constituents (eucalyptus, buchu, pilocarpus, etc.), they are of very 

 little value in the identification of powdered vegetable drugs. They 

 vary in size, number, position and abundance ; consistency and color of 

 contents. The contents may prove of diagnostic value. 



13. Petiole or Leaf Stalk. The petiole rarely presents any charac- 

 teristic elements. It is, histologically, similar to the stem or branches, 

 but, as a rule, less distinctively defined. The parenchyma cells usually 

 contain some starch, resin, crystals, coloring matter and other contents 

 common to stems of the same plant. Stone-cells or sclerenchyma-like 

 tracheids may prove diagnostic. There may be cork tissue present. 

 The vascular tissue is similar to that of the leaf blade. 



14. Lower Epidermis. Compare carefully with upper epidermis. 

 When stomata are wanting, it indicates the upper epidermis. 



2. FLOWERS 



Flowers, or parts of flowers, reduced to powder, are quite readily 

 recognized or identified, since, in addition to certain characteristic 

 histological elements (as epidermal cells, trichomes and pollen grains) , 

 there is, as a rule, a distinctive color, the predominating colors being 

 brown, yellow or yellowish, blue and red. 



1. Staminate Elements. The vegetable tissue of stamens is not 

 characteristic or diagnostic and need not be described more fully. 

 The important elements are the pollen grains. Carefully note form, 

 size and external markings (exine). They may vary greatly in size, 

 but the difference in form is usually more diagnostic. They may be 

 triangular, spherical or oval. Note carefully the markings of the 

 exine. The predominating color (exine) is brown to yellowish brown. 



