io8 



PHARMACEUTICAL BOTANY 



The epidermis of leaves, stems, fruits, and seeds of many plants 

 frequently give rise to outgrowths in the form of papillae, hairs 

 and scales. Epidermal papilla are short protuberances of epidermal 

 cells. They may be seen to advantage on the upper epidermis of the 



5 

 FIG. 46. FIG. 47. 



PIG. 46.' i, Epidermis of oak leaf ; 2, epidermis of Iris leaf, both viewed from 

 the surface; 3, group of cells from petal of Viola tricolor; 4, two epidermal cells 

 in cross-section showing thickened outer wall differentiated into three layers, 

 namely, an outer cuticle, cutinized layer (shaded), and an inner cellulose layer; 

 5 and 6, epidermal outgrowths in the form of scales and hairs, (i, 2, 6 after 

 Stevens, 3 after Strasburger, 4 after Sachs, and 5 after de Bary.) 



PIG. 47. Different forms of epidermal outgrowths, i, Hooked hair ffom 

 Phaseolus multiflorus; 2, climbing hair from stem of Humulus Lupulus; 3, cod- 

 Hke wax coating from the stem of Saccharum officinarum; 4," climbing hair of 

 Loasa hispida; 5, stinging hair of Urtica urens. (Fig. 3 after de Bary; the re- 

 mainder from Haberlandt.) 



ligulate corolla of various species of Chrysanthemum, on the lower 

 epidermis of the foliage leaves of species of Erythroxylon and upon the 

 upper epidermis of the petals of the Pansy (Viola tricolor}. Epi- 

 dermal hairs or trichomes are more elongated outgrowths of one 

 or more epidermal cells. They may be unicellular (Cotton) or 



