230 HISTOLOGY OF MEDICINAL PLANTS 
to 15.1 by 16.6 micromillimeters. The cell contents are dark 
and the walls are light. A few rows of the outer cortical paren- 
chyma cells of both the rhizome and the root have dark cell 
contents and white walls. The dark contents disappear toward 
the phloem. The cortical cells vary from 13.6 by 14.3 micro- 
millimeters to 89.5 by 90.9 micromillimeters. In the cortical 
parenchyma cells of the rhizome are found the short, broad 
cystoliths measuring up to 52 by 62 micromillimeters. In the 
corresponding cells of the root are found the long, narrow cysto- 
liths which measure up to 68.4 by 187.2 micromillimeters. 
Scattered throughout the powder are seen three distinct types 
of sclerids (stone cells) which are associated with the cortical 
parenchyma of both the stem and the root. Most of them are 
found, however, in the roots. First, the short, broad stone 
cells from the stem basis have square ends; the walls vary from 
13 to 19.5 micromillimeters in thickness with branching pores 
which extend toward the adjacent cell. These sclerids vary in 
size from 52 by 54.6 micromillimeters to 45 by 130 micromilli- 
meters. Secondly, the long stone cells from the root vary from 
32 by 96 micromillimeters to 45.5 by 542.5 micromillimeters 
with walls 16 micromillimeters thick. The width of the cell 
and the thickness of the wall vary but little throughout their 
entire length. The third type of stone cell also from the root 
has unequally thickened walls and the ends are square or blunt. 
A few long, narrow, colorless, thin-walled bast fibres also occur. 
They are 13 micromillimeters wide, with walls 3.9 micromilli- 
meters thick. Annular spiral and pitted vessels are also found 
scattered throughout the powder. 
The diagnostic characters of the powder are: 
1. The short, broad, and long, narrow cystoliths. 
2. The short, broad, and long, narrow sclerids. 
3. The long, narrow, thin, white-walled bast fibres. 
In poke root, ipecac, sarsaparilla, and veratrum are raphides. 
In belladonna and horse-nettle roots are micro-crystals. In 
calumba, stillingea, krameria, licorice, scamony root are prisms. 
In saponaria, jalap, althea, spikenard, rumex, rhubarb are 
rosette crystals. In pleurisy roots both prisms and rosettes 
occur. 
In gentian, senega, symphytuns, lovage, parsley, inula, 
