78 LEAVES, 



(43) Rue Leaves. 



The leaves of Ruta graveolens, Linn. (N.O. Rutaceae) 



The epidermis of the upper surface is glabrous, and composed 

 of large cells with undulating delicately pitted walls. The cells 

 of the lower epidermis, which is also glabrous, have sinuous walls. 



Stomata are to be found on the lower epidermis only ; they are 

 surrounded and partially overhung by four or five surrounding 

 cells which exhibit no regularity in shape or arrangement. 



The cells of the epidermis of the midrib also have pitted walls. 



The mesophyll is heterogeneous and asymmetrical ; the spongy 

 parenchyma contains numerous cluster crystals of calcium oxalate, 

 and in this tissue internal oil-glands are to be found. 



The midrib is concave on the upper surface, convex on the lower ; 

 the wood is crescent shaped and there are no fibres in either bast 

 or pericycle. 



The diagnostic characters of powdered rue leaves are : 



(a) The upper epidermis with pitted cell-walls. 



(b) The stomata. 



(c) The cluster crystals of calcium oxalate. 

 . (d) The oil-glands. 



(e) The absence of hairs and pericyclic fibres. 



