LEAVES. 



The presence of ridges on the surface of the cubicle imparts a 

 very characteristic appearance to the epidermal cells in surface 

 view ; these then exhibit more or less distinct striations, and this 

 becomes an important diagnostic character in the identification 

 of the powder (hemlock, jaborandi, belladonna). If the cuticle 

 bears protuberances these will appear in transverse section as 

 projections from the epidermal cells (which may also themselves 

 be papillose), but in surface view they are visible as not very 

 sharply defined circles, often near the middle of the epidermal 

 cell (coca). Occasionally a hypoderma consisting of one or more 

 layers of cells may be found (boldo), and this may afford a 

 useful indication of the identity of a leaf. 



Stomata. 



The arrangement of the stomata and the cells that surround 

 them furnishes a very valuable indication of the identity of the 

 powdered drug, especially as the character is a constant one. 

 Vesque, in his studies of the comparative anatomy of plants, 

 has shown to what extent this feature can be utilised. It 

 exhibits a remarkable constancy in the leaves of certain natural 

 orders, amongst which Labiatce, Caryophyllece, Rubiacece, 

 Apocynece, Malvactce, and Cruciferce may be mentioned. 

 It should be added, however, that if the arrange- 

 ment of the stomata is not found to be the same 

 in the leaves of all plants belonging to large natural 

 orders such as Legummosae, it is at least constant for all the 

 leaves of one species. If, therefore, the arrangement of the 

 stomata in any particular leaf is known, this character can easily 

 be utilised to identify the leaf when powdered. The shape of 

 the stomata should also be observed. Very often each stoma 

 is surrounded by three, four, or five cells that exhibit little 

 regularity in their shape or arrangement (Scrophularinece) ; on 

 the other hand in the leaves of many plants belong- 

 ing to the sub-order Papilionece of Leguminosce the stoma 

 is flanked on either side by a crescent-shaped cell 

 nearly parallel to the ostiole. This character occurs 

 still more uniformly in the leaves of Rvbiacece, Apocynacece, and 

 Asclepiadece. In the natural order Labiatce, the stoma 

 is regularly placed perpendicularly to the wall separating 

 two neighbouring cells (betony). This character can, 

 therefore, be utilised 1 in identifying the powders of leaves 

 belonging to this natural order. In carophyllaceous leaves the 

 stomata usually appear suspended from the wall dividing two 

 neighbouring cells from one another. 



