56 LEAVES. 



(32) Betony Leaves. 



The leaves of Bctonica officinalis, Linn. (N.O. Labiatse). 



The cells of the interneural epidermis are smooth, and have 

 slightly wavy walls; on both surfaces there are stomata and 

 simple as well as glandular hairs. Each stoma is enclosed between 

 two cells, the long axes of which are at right angles to tlie ostiole; 

 this arrangement is common amongst labiate leaves. 



The simple hairs are long, pluricellular, and conical ; they are 

 composed of from three to live cell" arranged in a single series; 

 these cells have strongly thickened walls. The hairs are enlarged 

 at the base, and are deeply inserted between the epidermal cells, 

 leaving a very conspicuous scar when they fall off. 



The glandular hairs vary in s'hape and structure. Some are very 

 small with rounded or oval bi-cellular glands borne upon a conical 

 pedicel, others are larger, sessile, and quadricellular . 



The mesophyll is heterogeneous and asymmetrical. The midrib 

 is concave above, convex below, and covered by a striated epidermis. 

 The wood is crescent-shaped ; there are no fibres in either bast or 

 pericycle. Betony leaf contains no crystals. 



The diagnostic characters of powdered betony leaves are : 



(a) The thick-walled conical hairs. 



(b) The stomata enclosed between two cells at right angles to the 

 <ostiole. 



(c) The glandular hairs. 



(d) The absence of crystals. 



<(e) The absence of pericy die fibres. 



