ROOTS AND RHIZOMES 227 
The wood parenchyma consists of thick-walled cells of irreg- 
ular size and form. 
The medullary rays are tangentially elongated and rectangular 
in form. 
Pith parenchyma. ‘The pith parenchyma cells are rounded 
in outline and as large as the cortical parenchyma cells. 
POWDERED PINK ROOT 
When the roots and rhizomes of spigelia are powdered (Plate 
93) they show the following structure: : 
The epidermal cells are small and brownish on surface view, 
varying in size from 13 by 18 micromillimeters to 31 by 4o 
micromillimeters. When associated with parenchyma they ap- 
pear as black masses. The cortical parenchyma cells are rounded 
and vary in size from 23 by 26 micromillimeters to 37.5 by go 
micromillimeters. Many of the cells from the root contain 
larger quantities of minute single rounded starch grains varying 
in size from 1 micromillimeter to 4 micromillimeters. The 
larger round single starch grains are found in both the cortical 
and pith parenchyma of the rhizome. ‘They vary in size from 
5 micromillimeters to 18 micromillimeters. The conducting 
elements are pitted tracheids varying from 10 micromillimeters 
to 38 micromillimeters in diameter. A few pitted and annular 
vessels are also found. The only fibres occurring are found in 
the xylem. They are not a prominent feature of the powder, 
as their walls break up into minute fragments. The pith 
parenchyma varies in size from 13 by 19 micromillimeters to 
75 by 82.5 micromillimeters. It is in these cells that the largest 
starch grains occur. 
Distinguishing diagnostic characters of the powder: 
1. Parenchyma with starch. 
2. Dark masses of epidermal tissue. 
3. Spigelia should contain starch, and it should not contain 
cystoliths, stone cells, or long, white-walled bast fibres. 
POWDERED RUELLIA ROOT 
When the roots of ruellia root and rhizome are powdered 
(Plate 94) they show the following structure: 
The epidermal cells vary from 7.8 by 15.6 micromillimeters 
