262 RHIZOMES AND ROOTS. 



(126) Senega Root. 



The root of Polygala Senega, Linn. (N.O. Polygalese). 



The root is sometimes normal in structure, but more fre- 

 quently it exhibits abnormalities due partly to the irregular 

 activity of the cambium and partly to the development of 

 parenchymatous tissue in place of normal wood. The trans- 

 verse section of a normally developed root exhibits a circular 

 wood, composed of vessels and tracheids, surrounded by a rather 

 thick ring of bast and cortex. In abnormally developed roots, 

 semi-circular or wedge-shaped portions of the wood consist of 

 parenchymatous tissue, and the bast ring and cortex are so 

 strongly developed on one side, usually that opposite to the 

 parenchymatous wood, as to form a projecting ridge. 



The cork is composed of cells, which, in surface view are 

 either elongated (root) or polygonal (crown of the root). 



The cortex is narrow in the ridge, but a little wider on the 

 opposite side of the root ; it is composed of parenchymatous cells 

 with rather thick walls. 



The bast ring is wide and usually very strongly developed on 

 he side opposite to the abnormal part of the wood. 



The wood is composed normally of pitted vessels and 

 tracheids, but does not exhibit medullary rays. The abnormal 

 wood consists of parenchymatous cells. The parenchymatous 

 tissue of both wood and bast contains minute droplets of oil, 

 but neither starch nor calcium oxalate. 



The diagnostic characters of powdered senega roo are : 



(a) The absence of starch and calcium oxalate. 



(b) The presence in the parenchymatous cells of minute 



droplets of oil. 



(c) The abundant tracheids and parenchymatous 



(d) The absence of sclerenchymatous cells and bast fibres. 



