248 RHIZOMES AND ROOTS. 



(119) Marshmallow Root. 



The root of Alttuea officinalis (N.O. Malvaceae). 

 The root presents the following structure : 



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

 surface view, are polygonal and isodiametric. 



This part of the root is often removed by scraping ; the finer 

 qualities of powdered marshmallow root do not therefore contain 

 any cork, but in the lower qualities, such as are used for 

 veterinary medicines, it is almost always to be found. 



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

 together with an occasional rosette of calcium oxalate. The 

 starch grains are mostly simple and oval or elongated in shape, 

 measuring from 4 to 15/j. in length ; here and there compound 

 grains with three or four component grains may be detected. 

 Distributed throughout the cortex, and, indeed, through all the 

 parenchymatous tissue of the root, are numerous cells filled with 

 mucilage ; these cells are rather larger than the surround- 

 ing parenchymatous cells, and the mucilaginous contents may 

 be detected by examination in alcohol or by staining with 

 solution of ruthenium red in lead acetate. 



(3) Bast Ring, which is particularly characterised by the pre- 

 sence of numerous tangentially elongated groups of bast fibres. 

 These fibres are very long, and their walls, which are not very 

 thick, are only slightly lignified. 



(4) Wood, in which the parenchymatous tissue is largely deve- 

 loped. The vessels are not numerous, they are either single or in 

 small radially elongated groups, accompanied by a few thin- 

 walled tracheids and surrounded by wood fibres. The parenchy- 

 matous cells contain either starch grains, or rosettes of calcium 

 oxalate, and, as already observed, numerous mucilage cells are 

 scattered throughout this tissue, as also throughout the cortex 

 and bast-ring. 



The diagnostic characters of powdered marshmallow root- 

 are : 



(a) The numerous mucilage cells. 



(b) The small starch grains. 



(c) The long bast fibres with moderately thick walls. 



