134 PLANT ORGANS OR PARTS OF PLANTS. 



small intercellular spaces and numerous clearly marked 

 starch grains with eccentric hilums. The cortex con- 

 tains a number of secretory reservoirs which are about 

 the shape and size of the parenchyma cells, or slightly 

 larger; the cell walls of these are suberized and they 

 contain yellowish ethereal oil, which at times becomes 

 resinous. Numerous small calcium oxalate crystals 

 are present. 



The fibro-vascular bundles of the cortex are rudi- 

 mentary or built on the same plan as those inside the 

 endodermis. The endodermis is composed of one to 

 three layers of much contorted, slightly elongated cells 

 whose walls are comparatively thick, compressed, and 

 somewhat suberized. Some annular reticulated vessels 

 are often found close to the endodermal sheath. 



The central portion consists mainly of parenchymatic 

 tissue similar to that in the cortex. The fibro-vascular 

 bundles are of the closed collateral type. The xylem 

 consists of from three to eight tracheids and a few spiral 

 vessels or spiral-like tracheids.* These are surrounded 

 in part by a varying number of sclerenchymatic elements 

 with pores with cross partitions which are slightly lig- 

 nified. These elements are more numerous on the tracheal 

 side of the bundle. At times they surround the bundle 

 completely. Secretory cells are sometimes found in this 

 portion of the rhizome. The phloem is made up of 

 parenchyma and a few sieve tubes with oblique walls, 

 surrounded by parenchyma cells. 



The starch of ginger is of diagnostic importance. In 

 the powder the presence of much corky tissue is indica- 

 tive of the fact that the outer rind has not been removed. 



Adulterations of powder are not rare. 



Chemistry. — Two to six per cent, ethereal oil, Ter- 

 pene, Acid, three to five per cent. ash. 



* A. Mayer: Arch. d. Ph., 1881, S. 422. 



