MICROSCOPICAL EXAMINATION OF POWDERED VEGETABLE DRUGS 85 



somewhat elongated in a direction radial from the base of the hair- 

 cells. The number and form of these neighboring cells may occasion- 

 ally prove diagnostic. 



In the case of glandular hairs, the size and number of end cells 

 or secreting cells may be diagnostic. Under this group must also 

 be included those structures more specifically designated as glands 

 (kamala, lupulin, Grindelia robusta) , and emergencies. 



4. Stomata. The stomata themselves are of no practical diagnostic 

 significance. In the case of typically dorsi ventral leaves they are 

 wanting in the upper epidermis. In the more or less isolateral leaves 

 there are stomata on both surfaces. In some instances it is possible 

 to distinguish between upper and lower epidermis by the number of 

 stomata. The size and form of the guard-cells is quite uniform in the 

 different species of plants. In leaves having an excessively thickened 

 cuticle, as eucalyptus, ficus and others, the guard-cells are not readily 

 observed. Rarely do these cells have any diagnostic or characteristic 

 contents; generally they contain chlorophyll and occasionally some 

 resin. 



5. Neighboring Cells. While, the stomata themselves present 

 little that is significant in the identification of drugs, the neighboring 

 cells (Nebenzellen) present some very striking diagnostic features, and 

 they should, therefore, be studied with great care. The number to 

 each stoma varies from two to five or six. In India senna, for ex- 

 ample, there are, as a rule, two cells, one much larger than the other. 

 The cells may contain resin, crystals and other substances not found 

 in the guard-cells or normal epidermal cells. The cuticular markings 

 may be different. The form of the outer wall may be different. In 

 coca leaves they do not have the wart-like projections so characteristic 

 of the normal epidermal cells. 



6. Air Chamber. The air chambers of the stomata are of no signifi- 

 cance. As a rule, the cells bounding the space contain crystals of 

 calcium oxalate, usually of the aggregate form. 



7. Hypoderm. Usually a hypoderm is wanting, and, when present, 

 is rarely of importance in powders. As a rule, the cells are colorless, 

 empty and well broken in the powdering. In ficus and other plants, a 

 few of the cells contain cystoliths. In buchu the cell-walls are muci- 

 laginous. They may contain crystals. The cells of the lower hypo- 

 derm are usually smaller than those of the upper. Again, the lower, 

 hypoderm may be entirely wanting, as in buchu. 



8. Palisade Tissue. This tissue is rarely of any significance in 

 powders, as the cell- walls are delicate and well broken. They all 

 resemble each other in containing an abundance of chlorophyll. They 

 vary considerably in length and in transverse diameter. 



