266 EHIZOMES AND ROOTS. 



(128) Turpeth Root. 



The rhizome and root of Convolvulus Turpethum, R. Brown 

 (N.O. Convolvulacese). The commercial drug consists of both 

 rhizome and root. 



The rhizome presents the following structure : 



(1) Cork, composed of several rows of tabular cells which, in 

 surface view, are polygonal and isodiametric. 



(2) Cortex, the cells of which are polygonal and contain starch 

 and calcium oxalate. The starch grains are either simple or 

 compound ; the former are rounded ; the latter often contain a 

 considerable number of component grains, which vary in shape, 

 according to the position they occupy in the grain. The 

 calcium oxalate occurs in rosette crystals of variable size, some- 

 times singly, sometimes several together in a cell. 



(3) Bast Ring, which is largely developed and contains nume- 

 rous rounded resin cells, as well as an abundance of calcium 

 oxalate. The outer part of this tissue is characterised by the 

 presence of sclerenchymatous pericyclic cells with moderately 

 thick walls. 



(4) Wood, which is divided into two bundles by two wide 

 medullary rays. It is composed of thick-walled pitted fibres 

 pitted and reticulate vessels and wood parenchyma. 



Old rhizomes are characterised by the presence of abnormal 

 bundles in the cortex ; in these the wood is surrounded by a 

 wide bast ring in which there are numerous resin cells. 



The root differs from the rhizome in the fact that the bast 

 ring is free from sclerenchymatous cells, and that the wood is 

 divided into five bundles by as many rather wide medullary 

 rays. 



The diagnostic characters of powdered turpeth root are :-- 



(a) The resin cells. 



(b) The starch. 



(c) The rosette crystals of calcium oxalate and their 



distribution. 



(d) The pitted ivood fibres. 



