60 LEAVES. 



(34) Buchu Leaves. 



The leaves of Barosma betulina, Bart, and Wendl. (N.O 

 Rutacese). 



The epidermis of the upper surface consists of polygonal cells, 

 nearly every one of which contains sphoerocrystalline masses or 

 feathery tufts of hesperidin ; these dissolve in caustic potash with 

 the production of a yellow colour. The cells also contain mucilage 

 which is deposited on the inner side of the inner tangential wall. 



The epidermis of the under surface is composed of similar cells, 

 which also contain hesperidin, but less mucilage. Both surfaces 

 are glabrous save for the occasional occurrence of a short, one-celled, 

 thickwalled conical hair near the midrib. 



The mesophyll is heterogeneous and asymmetrical ; it contains 

 rosette crystals of calcium oxalate and here and there a large 

 oil-gland. 



The midrib is concavo-convex in section. The wood is fan 

 shaped ; below the bast there is a crescent of pericyclic fibres 

 which vary in the extent of their thickening and lignification. In 

 the cortical tissue, which contains but little colleiichyma, there is 

 often a large oil-gland. 



The diagnostic characters of powdered buchu leaves are : 



(a) The polygonal cells of the epidermis with crystalline masses 

 *of hesperidin. 



(b) The abundance of mucilage. 



(c) The presence of pericyclic fibres. 

 ^d) The calcium oxalate in rosettes. 



