236 RHIZOMES AND ROOTS. 



(113) Hydrastis Rhizome. 



The rhizome of Hydrastis canadensis, Linn. (N.O. Ranun- 

 culacese). 



The commercial drug usually consists of the rhizome to 

 which a number of wiry roots are attached. 



The rhizome presents the following structure : 



(1) Cork, composed of several layers of brown, tabular cells 

 which, in surface view, are polygonal and isodiametric. 



(2) Cortex, the cells of which are rounded, thin-walled, and 

 exhibit intercellular spaces. In longitudinal section these 

 cells are axially elongated. They are filled with small starch 

 grains, either simple or united three or four together into com- 

 pound grains. 



(3) Bast Ring, traversed by wide medullary rays and almost 

 always destitute of fibres. 



(4) Wood, consisting of radially elongated wood bundles sep- 

 arated by very wide medullary rays. Each bundle is composed 

 of pitted vessels and tracheids, often filled with an amorphous 

 substance, narrow wood fibres and non-lignified thin-walled 

 parenchyma. 



(5) Pith, the cells of which are rounded and full of starch. 



The structure of the root is different. The epidermis is com- 

 posed of axially elongated cells ; the cortex is separated from 

 the stele by a conspicuous endodermis, the cells of which have 

 sinuous walls. The wood is represented by a ring of pitted 

 vessels which encloses a pith and is surrounded by groups of 

 bast tissue as well as by the pericycle. 



Most of the elements of both rhizome and root are character- 

 ised by a more or less pronounced yellowish colour. 



The diagnostic characters of powdered hydrastis rhizome 

 are : 



(a) The pervading yellowish colour. 



(b) The minute starch grains. 



(c) The absence of calcium oxalate crystals. 



(d) Tlie nature of the elements of the wood. 



(e) The absence of sclcrenchymatous cells. 



