116 HISTOLOGY OF MEDICINAL PLANTS 



stone cells of witch-hazel bark and leaf, wild cherry, etc., also 

 occur broken in the powder. 



The walls of all stone cells are composed of lignin. 



The form of stone cells varies greatly; in aconite the stone 

 cells are quadrangular; in ruellia they are rectangular; in 

 pimenta, circular or oval in outline; in most stone cells they 

 are polygonal. 



The lignified walls of stone cells are stained red with a 

 solution of phloroglucin and hydrochloric acid, and the walls 

 are stained yellow by aniline chloride. 



ENDODERMAL CELLS 



The endodermal cells of the different plants vary greatly 

 in form, color, structure, and composition of the wall, yet these 

 different endodermal cells may be divided into two groups: 

 first, thin-walled parenchyma-like cells, and, secondly, thick- 

 walled fibre-like cells. In the thin- walled endodermal cells the 

 walls are composed of cellulose, and the cell terminations are 

 blunt or rounded. When the drug is powdered the cells break 

 up into small diagnostic fragments. In the thick-walled endo- 

 dermal cells the walls are lignified and porous, and the ends of 

 the cell are frequently pointed and resemble fibres. 



Sarsaparilla root, triticum, convallaria, and aletris have 

 thick- walled endodermal cells. 



STRUCTURE OF ENDODERMAL CELLS 



The endodermal cells of sarsaparilla root (Plate 35, Fig. i) 

 are never more than one layer in thickness. The walls are 

 porous and of a yellowish-brown color. Alternating with the 

 thick-walled cell is a thin-walled cell, which is frequently re- 

 ferred to as a passage cell. 



The endodermal cells of triticum (Plate 35, Fig. 2) are yellow- 

 ish and the walls are porous and striated. There are one or two 

 layers of cells. The cells forming the outer layer have very 

 thin outer but thick inner walls, while the cells forming the 

 inner layer are more uniform in thickness. 



The endodermal cells of convallaria (Plate 35, Fig. 3) are 

 yellowish white in color, and the walls are porous and striated. 



