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uniformly applied and interpreted by all analysts. This does not 

 appear to be the case as may be ascertained from a comparison of the 

 terms used by the several authors on plant histology and pharmacog- 

 nosy. It is suggested that the student give special attention to the 

 study of fully formed or matured tissues and tissue elements according 

 to the following tabulated outline. This work may be taken up as a 

 preliminary preparation to the micro-analytical examination of vege- 

 table drugs and spices, crude as well as powdered. The terminology 

 as it applies to cell-contents such as starches, proteids, oils, fats, 

 crystals, etc., is but little confused. 



Tabulation of the Principal Vegetable Tissues 



TRICHOMES OB HAIR CELLS. (These belong to the epidermal tissue). 

 The following are the principal kinds : 



Simple : Single-celled; varying from very short to very long, walls 

 thick or thin, smooth or rough, warty, etc., as cotton, in tea 

 leaves,' sage, wheat, rye, apricot, quince, peach, strawberry, 

 raspberry, loganberry, etc. 



Many-celled: (usually two to five-celled) ; varying from short to 

 very long; cellwalls usually quite thin; smooth, roughened, warty, 

 etc., as in digitalis, aconite, mints, tobacco, belladonna, and in 

 many other vegetable substances. 



Aggregate or Stellate : As in mallows, castanea, hamamelis. 



Branching : Typically developed in mullein. 



Glandular : Trichomes with secreting end cells. End cells vary in 

 number from one, two and more, commonly five to ten as in the 

 mints, tobacco, hyoscymus, nettle, etc. The number of secreting 

 cells is occasionally diagnostic. The multicellular structures of 

 kamala and lupulin are usually designated as glands. 



Multicellular: More than one row or layer of cells, as in cocoa, 

 Indian hemp (multicellular glandular trichomes) , rhus glabra fruits, 

 etc. Not common nor widely distributed in the plant kingdom. 

 True Multicellular Trichomes: As in rhus glabra. 

 False Multicellular Trichomes or emergencies; as in Indian 

 hemp. Pappus, prickles, warty excrescences and similar 

 structures should be included here. 



Unusual Trichomatic Structures: T-shaped as in Pyrethrum 

 flowers; shield-form as in the olive leaf, etc. Naturally such 

 unusual structures are highly diagnostic. None of the U. S. P. 

 drugs contain any of the very unusual trichomatic structures. 

 EPIDERMIS. In plants, a single layer of cells, bearing the above men- 

 tioned trichomes. Including also the outer layer, of the seed coat 



