62 LEAVES. 



(35) Coca Leaves. 



The leaves of Erythroxylon Coca, Lam. (N.O. Linese). 



The epidermis of the upper surface is composed of polygonal 

 cells covered with a rather thick, smooth cuticle; they measure 

 from 30 to 45;u in length, and from 15 to 30/x, in breadth. 



The lower surface is well characterised by the papillose develop- 

 ment of the epidermal cells. This peculiarity imparts a sinuous 

 outline to the lower epidermis' when seen in transverse section, 

 but in surface view the papillae appear as not very sharply defined 

 circles. Each stoma is accompanied by two cells, with their long 

 axes parallel to the ostiole ; these cells are not papillose. The 

 leaves are quite glabrous on both surfaces. 



The mesophyll is heterogeneous and asymmetrical ; the spongy 

 parenchyma is composed of stellate cells, some of which contain 

 prismatic crystals of calcium oxalate. 



The midrib is bi-convex. Under the epidermis of both surfaces 

 there is a rather thick layer of collenchymatous tissue. The wood 

 of the meristele is curved, and below it is the bast beyond which 

 again there is an arc of lignified pericyclic fibres ; there are also two 

 groups of similar fibres above the wood, one near each extremity. 



The cells next to the pericyclic fibres contain prismatic crystals 

 of calcium oxalate, as do also some of the cells of the cortical 

 parenchyma. 



The diagnostic characters of powdered coca leaves are : 



(a) The polygonal papillose cells of the lower epidermis. 



(b) The stomata accompanied by two cells with their long azes 

 parallel to the ostiole. 



(c) The presence of pericyclic jibrcs. 



(d) The absence of hairs. 



{e) The prismatic crystals of calcium oxalate. 



