216 . RHIZOMES AND ROOTS. 



(103) Aconite Root. 



The root of Aconitum Napellus, Linn. (N.O. Ranunculacese). 

 The root presents the following structure : 



(1) Tegumentary Tissue (metaderm), composed of brown 

 tabular cells which in surface view are polygonal and of 

 variable size and shape. 



(2) Cortex, consisting of polygonal parenchymatous cells 

 filled with starch ; many of the cells also contain the brownish 

 remains of protoplasm. Numerous sclerenchymatous cells, 

 occasionally strongly elongated, with thickened, pitted walls, 

 are scattered throughout this tissue. 



(3) Endodermis, which is very conspicuous. It consists of a 

 single row of rectangular, tangentially elongated cells with 

 slightly thickened and often brownish walls. 



(4) Bast Ring. This tissue is rather largely developed. Towards 

 the exterior it is composed, of irregular polygonal cells that do 

 not exhibit any definite arrangement, but as the wood is 

 approached they become more regular, isodiametric and assume 

 a radial arrangement. It contains numerous groups of sieve 

 tissue but no bast fibres. 



(5) Wood, separated from the bast ring by a stellate cambium 

 with about seven angles in which there are fibro vascular 

 bundles of varying dimensions, those in the angles that 

 project into the bast ring being larger than the others. The wood 

 consists principally of parenchymatous tissue, the cells of which 

 contain an abundance of starch in simple and compound 

 grains ; the former are rounded ; the constituent grains of the 

 latter vary in shape according to the number in the compound 

 grain, and are usually rounded on one side and angular on the 

 other. There is no calcium oxalate present. 



The diagnostic characters of aconite root are : 



(a) The starch grains. 



(b) The presence of sclerenchymatous cells, but absence of 



bast fibres. 



(c) The brownish contents of many parenchymatous cells. 



(d) Absence of calcium oxalate 



