84 POWDERED VEGETABLE DRUGS 



the epidermal cells in profile view. Trichomes usually appear more 

 or less broken ; 



2. Upper Epidermis. Carefully note the general form of the 

 cells as determined from an examination of transverse and tangential 

 (surafce) sections. Make careful measurements of normal or typical 

 cells, remembering that epidermal cells lying over vascular bundles 

 .(of veins and midril) are considerably elongated. The outer walls of 

 the cells or cuticle should be examined in transverse view to note 

 thickness and special modifications, resinous or waxy deposits, etc., 

 also in vertical view to note presence or absence of warty, linear or 

 other cuticular markings, which may prove diagnostic. The vertical 

 walls may be straight and distinct, somewhat variable in thickness; 

 more rarely porous and nodular, as in buchu. In many leaves the 

 vertical walls are wavy instead of straight, and these differences are 

 occasionally diagnostic. As a rule, epidermal cells have few important 

 or diagnostic contents. Occasionally crystals of calcium oxalate are 

 found; also a few chlorophyll granules. They may contain resin 

 (pilocarpus), inulin and hesperidin (buchu), also a small amount of 

 starch, tannin and coloring matter. In brief, note carefully form and 

 size of the cells; thickness of cuticle, cuticular markings; and occa- 

 sional possible diagnostic cell-contents. 



3. Trichomes or Hair-Cells. Trichomes or hair-cells are very 

 important and diagnostic. These, more than any other elements, 

 are the means of identifying the substance having such structures. 

 The non-glandular trichomes are especially diagnostic. The glandular 

 hairs are, as a rule, small and delicate, and their identity is often 

 lost in the powdering. The non-glandular hairs are divided into 

 single celled, many celled, stellate or aggregate and branching. Study 

 these carefully as to length, diameter, form (curved, inclined, erect), 

 thickness of walls and cuticular markings, rarely also color and contents 

 (Cannabis Indica). Length is very variable in different plants for 

 example, single-celled trichomes vary from mere wart-like outward 

 projections of the outer walls of epidermal cells, as in coca leaves and 

 anise, fruit, to the long (1 to 3 inches) fibres of the cotton seed. The 

 many-celled simple trichomes (usually 3 to 5-celled) also differ in 

 length, but vary more diagnostically in width. Occasionally the 

 number of trichomes is more or less diagnostic (Alexandria and India 

 senna). Aggregate and branching hairs are very striking in appear- 

 ance and hence highly diagnostic. 



Each hair-cell, which is simply a modified epidermal cell, is sur- 

 rounded by epidermal cells (neighboring cells) which generally differ 

 somewhat from other or normal epidermal cells. As a rule, they are 



