80 . POWDERED VEGETABLE DRUGS 



or testa in which the cells often show remarkable structural varia- 

 tions. The cells differ greatly as to size and form, thickness and 

 structure of cell-walls, as to cell-contents, etc. Note especially 

 epidermal cells of leaves; of fleshy fruits (of tomato, window cells 

 of apple and quince); the papillose cells of coca leaves and rose 

 petal; of young stems, etc. 



Cuticle : The outer or external cell-wall, with various markings 

 and projections. Extremely variable as to thickness. The inner 

 wall of epidermal cells (the wall parallel to the cuticle or outer 

 wall) never presents any diagnostic characters and need not be 

 further mentioned. 



Vertical Cell-Walls: These may be wavy (sinuous), or straight; 

 thin, much thickened, warty, porous. 



Stomata: Somewhat variable as to size of guard cells but the 

 structural differences are not sufficiently marked to be of any 

 special diagnostic value. The relative occurrence and distribu- 

 tion of stomata on upper and lower surfaces of bifacial (dorsiver- 

 tral) leaves will occasionally prove diagnostic. 



Nebenzellen (Neighboring Cells) : May be of great diagnostic value, 

 indicated by number of cells, size and form of the cells and nature 

 of cell-contents. 



HYPODERM. One or more layers of cells immediately underneath 

 the epidermis, as in buchu, mace, fig. The cells are usually much 

 larger than those of the epidermis but quite generally without 

 diagnostic structural characters or contents (cystoliths in fig 

 leaf). Cell- walls may be mucilaginous as in buchu. Not common. 

 COLLENCHYMA. Characterized by cell-walls thickened at the angles. 



Parenchymatous : Cells nearly isodiametric or slightly elongated, 

 as in gentian root. 



Bast-like : Cells much elongated, the usual or typical form, as in 

 labiate stems. The characteristic thickenings at the angles of 

 the cells are seen in transverse section. 



PALISADE TISSUE OR CELLS. Elongated cells usually placed endwise, 

 vertically to surface; as the palisade tissue of the leaves, of the 

 seed coat (testa of many seeds, bean, pea, apple seed, quince 

 seeds, etc.). Generally of great diagnostic value, .excepting in 

 case of leaf palisade which is only exceptionally diagnostic. 

 BAST CELLS OR BAST FIBERS. Elongated cells. Cell-walls with or 

 with out lignin; comparatively non-porous; ends tapering pointed. 



Typical: Greatly elongated cells; extremely flexible; colorless; 

 usually non-lignified but much thickened walls. Typically devel- 



