88 POWDERED VEGETABLE DRUGS 



In the case of seeds the epidermal cells undergo remarkable and varied 

 modifications. They may be trichomatic, filamentous, as in strophan- 

 tus, nux vomica, cotton seed; gelatinized and palisade-like, as in 

 cydonia; sclerenchymatous, as in almond seeds, besides other peculiar 

 modifications. Owing to the predominance of endosperm tissue epider- 

 mal elements are sparingly distributed through the powder, and for 

 this reason a very careful study is necessary to find the sparingly pres- 

 ent, but perhaps very diagnostic elements. 



2. Stone-Cells. These are often abundantly present. In form 

 they vary from typical to elongated bast-like, as in the pericarp of 

 Cassia fistula and the seed of Caffea. In color they vary from deep 

 reddish-brown to nearly colorless. Usually they occur in groups, 

 sometimes singly (almond, pepo), and in some instances they are very 

 sparingly present. The thickness and porosity of cell-walls is quite 

 variable and should be considered. In some instances the wall of 

 one side of the cell is thinner than that of the others. 



3. Special Tissues of Testa. Most of these special tissues have a 

 purely mechanical function. Some are sclerenchymatous (Cydonia); 

 some carry prismatic crystals of calcium oxalate (bean). Other 

 tissues consist of thin-walled cells and are much broken in the powders. 

 The cells may vary in form; they may be tabular, elongated, cubical 

 or hour-glass form. They are rarely diagnostic. 



4. Endosperm Tissue. This is essentially parenchymatous and 

 constitutes the predominating tissue of seeds. The cells vary in thick- 

 ness of the walls; also in porosity and in the character of localized 

 thickenings. As to form the cells of the endosperm tissue are mostly 

 typical of parenchyma; they may be rectangular, elongated. While 

 the variation in size may be considerable, it will be found that this 

 difference proves to be only of occasional diagnostic value. The 

 peripheral cells are, as a rule, smaller than the more internal ones. 



The cell-contents should be studied with great care. Note es- 

 pecially the absence or presence of starch. Be careful not to confuse 

 proteid granules with starch granules (almond, croton and castor 

 beans). Look for resin-bearing cells. Oils and fats are generally 

 present. Occasionally crystals may be found. Vascular tissue is 

 quite deficient in seeds and rarely, if ever, diagnostic. 



Oil cells and resin-bearing cells may occur in the endosperm, in 

 the pericarp and in other seed and fruit parts. These are, as a rule, 

 very diagnostic, and should be studied carefully as to number, size, 

 form and color of contents. 



5. Parenchyma of Pericarp. This is generally a typical par- 

 enchyma. Compare with parenchyma of roots and rhizomes. Usually 



