MICROSCOPICAL EXAMINATION OF POWDERED VEGETABLE DRUGS 93 



9. Pith. Usually present, but not specially diagnostic. Note 

 cell aggregations (rosettes) and cell-contents, as resin, mucilage, crystals 

 and starch. 



10. Vascular Elements. See "Roots and Rhizomes." 



7. WOODS 



There are only a few employed, and are quite characteristic in 

 color, as the straw-yellow quassia, olive-green guaiac, red sandalwood, 

 purplish haematoxylon and reddish-brown sassafras. 



1. Wood Cells. Note diameter, thickness of walls, and contents 

 as starch, resin and crystals. 



2. Ducts. Note presence or absence, diameter, porosity and other 

 markings. Often diagnostic. 



3. Medullary Rays. Important and often diagnostic. Note num- 

 ber of cell-rows, porosity of cell- walls, and cell-contents. 



8. OTHER PLANT PARTS 



Under this head are included ergot and corn smut (fungi) ; dextrin 

 (modified starch); Kamala (trichomes and glands); Lycopodium 

 (spores of club-moss) ; Iceland moss (lichen) ; Irish moss (marine alga) ; 

 starches, cereal flour, resin, waxes, gums, etc., etc. These must be 

 studied with great care as to minute details of structure. 



IV. TABULATION OF TISSUES AND TISSUE ELEMENTS 



The following summarizing of plant organs with their characteristic 

 tissues and tissue elements will be found useful and suggestive in the 

 critical histologic examination and study of crude drugs and powdered 

 drugs. 



I. LEAVES. 



I 1 Epidermal elements. By far the most important diagnostic 



elements of the leaf. 

 I 2 Upper epidermis. 

 I 3 General outline of cells as determined from an examination 



of transverse and surface sections. 

 2 3 Measurements. Size of cells sometimes diagnostic. ' 

 3 3 Cuticle. 



I 4 Thickness. Very variable. 



2 4 Surface markings. Linear, warty, none. 



3 4 Surface deposits. Resinous, waxy, none. 



