MICROSCOPICAL EXAMINATION OF POWDERED VEGETABLE DRUGS 83 



Elongated, narrow conducting cells usually accompany the sieve 

 tubes. These are rarely of diagnostic value. 



CRYSTAL BEARING FIBERS. Rectangular cells united end to end form- 

 ing elongated threads, each cell bearing a prismatic crystal of 

 calcium oxalate. Usually associated with bast tissue. Typically 

 developed in cascara bark and other barks, licorice root, etc. 



LACTICIFEROUS DUCTS. Typically developed in the fig and dandelion. 

 Also found in other plants. Highly diagnostic of the fig. 



RESIN DUCTS. Typically developed in the bark and wood of the coni- 

 ferse. 



GLANDS. As in leaves (buchu, eucalyptus, pilocarpus, bay, etc.), 

 in some barks, fruits, seeds, etc. 



GLANDULAR CELLS. As in mace, elm bark, canella bark, allspice, ginger, 

 etc. Usually contain mucilage, resin, oleo-resin and oil. Size 

 of cells, relative number of cells and character of cell-contents 

 often very diagnostic. 



ATYPICAL CELLS AND TISSUES. Essentially fomative or immature and 

 of very little diagnostic value. Includes the so-called phloem 

 tissue, cambium, cork cambium, phellogen, so-called conducting 

 cells of the phloem portion of vascular bundles, apical cells, and 

 immature cells generally. 



III. OCCURRENCE AND DISTRIBUTION OF TISSUE ELEMENTS IN PLANT 



ORGANS 



The following suggestions are to be considered carefully, as a 

 rather full knowledge of those tissue elements and cell-contents which 

 are most likely to retain their individuality after powdering, or which 

 will prove diagnostic, will simplify the work of studying and identifying 

 vegetable powders. 



1. LEAVES 



Under this head are included leaves, leaflets, herbs, and flowering 

 tops in which leaves predominate. The predominating color of 

 leaves when powdered is green, due to the presence of chlorophyll. In 

 some instances the color merges into brown or yellowish-brown, as in 

 coca and pilocarpus. 



1. Epidermal Elements. -By far the most important diagnostic 

 elements of the leaf are the epidermal, inclusive of trichomes, stomata 

 and Nebenzellen (neighboring cells). The epidermal elements being 

 the more resisting parts of the leaf are not so readily reduced in 

 powdering and appear in cell-aggregates of tabular form, presenting 

 mostly a vertical view; rarely one may also find fragments showing 



