and Laboratory Methods. 



•2521 



in common. We have known the powder of the one to be mistaken for the other. 

 A lantern slide prepared of the mixture of the two powdered leaves serves only, 

 however, to show how to distinguish the histological elements in a mixed powder, 

 although these elements may be mainly of leaf fragments, and serves also to 

 illustrate the principles of identification by microscopical study of histological 

 elements. 



By referring to the figure it will be seen that we have from Alexandria senna : 

 (a) epidermis ; (g) epidermis from savine. These epidermal cells when com- 

 pared, as to the shape and size of the stomata and the shape and character of 

 the epidermal c§ll walls, furnish a means of distinguishing the two leaves without 



MIXED DRUG POWDERS. 



(a) Epidermis showing stomata from Alexandria senna. 



(b) Trichomes from Alexandria senna, 

 (p) Stone cells from savine. 



( j ) Bast fiber from savine. 



( 1 ) Parenchyma cells from savine. 



(e) Parenchyma cells with calcium oxalate crystals from Alexandria senna, 

 (d) Annular ducts and sclerenchyma fibers from Alexandria senna. 



(g) Epidermis with stoma from savine. 



(c) Crystal fiber and sclerenchyma from Alexandria senna, 

 (m) Sclerenchymatous cells with bordered pits from savine. 



(f ) Crystals of calcium oxalate from Alexandria senna, 

 (k) Epidermis — lateral view — from savine. 

 Magnified, 173 diameters. 



effort. If now, we look for other histological elements, first of senna, we see the 

 hairs at (b), the crystal bearing fiber at (c), the parenchyma cells bearing calcium 

 oxalate crystals at (e), and isolated crystals of calcium oxalate at (f). On the 

 other hand, we have from savine sclerenchymatous cells with bordered pits at (m), 

 long, slender bast fibers at (j), and stone cells at (p), which furnish ready means 

 for illustration by which students may easily comprehend the subject and under- 



