232 RHIZOMES AND ROOTS. 



(Ill) Ginger Rhizome. 



The rhizome of Zingiber officinale, Roscoe (N.O. Scitaminese). 



The rhizome presents the following structure, but the epi- 

 dermis, hypoderma, cork and part of the cortex are often 

 removed by peeling ; this is particularly the case with Jamaica 

 ginger. 



(1) Epidermis, the cells of which are polygonal and thin- 

 walled. 



(2) Hypoderma, subjacent to the epidermis and consisting of 

 a few rows of polygonal cells. 



(3) Cork, of which there are usually several rows ; the cells 

 are rather large and thin-walled. 



(4) Cortex , composed of polygonal, thin-walled, parenchy- 

 matous cells, most of which are filled with starch grains, but 

 some contain yellowish-brown oleoresin, and these have 

 suberised walls. 



(5) Stele, resembling the cortex in structure. Both cortex 

 and stele are traversed by numerous fibrovascular bundles 

 which contain a few reticulated vessels, and are supported by a 

 crescent-shaped mass of sclerenchymatous fibres, some of which 

 are chambered. Narrow, axially elongated cells, containing a 

 dark brown secretion, are occasionally to be seen abutting on 

 the vessels. 



The starch grains are very characteristic. They are simple 

 and of considerable size, measuring 12 to 30^ in length ; they 

 are somewhat, but not strongly, flattened, and exhibit an ovoid, 

 trapezoidal or sack-shaped outline ; the striations are faint but 

 frequently discernible. 



Most of the oleoresin cells are broken during pulverisation 

 and their contents escape ; a few, however, remain intact. 



The diagnostic characters of powdered ginger are : 



(a) The starch grains ; their number, size and shape. 



(b) The oleoresin cells. 



(c) The sclerenchymatous fibres. 



(d) The thin-walled parenchymatous cells. 



