64 LEAVES. 



(36) Foxglove Leaves. 



The leaves of Digitalis purpurea, Linn. (N.O. Scrophularinese). 



The epidermis of the upper surface is composed of polygonal 

 cells from 30 to 60^ long with slightly wavy walls and a smooth 

 cuticle ; that of the lower surface is similar, but the walls of the 

 cells are more wavy. Both surfaces bear stomata and simple as 

 well as glandular hairs. 



The stomata are surrounded by three or four cells, which exhibit 

 no regularity in either shape or arrangement. 



The simple hairs are pluricellular and conical ; they consist of 

 from three to five cells with thin walls, the latter being sometimes 

 smooth, sometimes slightly warty. These cells sometimes collapse 

 and present alternately a narrow edge and a flattened surface to 

 the observer. 



The glandular hairs are shorter, and composed of from one to 

 three cells with a unicellular or Hcellular gland. 



The mesophyll is heterogeneous, asymmetrical, and destitute of 

 crystals. 



The midrib, which is very strongly convex below, is also furnished 

 with simple and glandular hairs. The wood is crescent-shaped, 

 and neither bast nor pericycle contain any lignified elements. 



The diagnostic characters of powdered foxglove leaves are : 



(a) The characteristic hairs. 



(b) The sinuous epidermal cells with small stomata. 



(c) The absence of pericy die fibres. 



(d) The absence of calcium oxalate crystals. 



