MEMOIRS FROM THE DEPARTMENT OF BOTANY OF COLUMBIA COLLEGE. 167 
cylinder and the xylem make the pleromatic part a strong sheath measuring from 
100 to 350 uw. 
The cuticle is conspicuously ribbed or longitudinally furrowed between the epider- 
mal elements. The epidermis is composed of one row of oblong-prismatic cells, which in 
cross section are quite irregular, and the long diameter is often radial, in this, as well as 
in their irregular prismatic shape, differing from most of the other species examined ; 
their height varies from 50-70 u. Trichomes occur as long bristle-like hairs, are unicell- 
ular and more or less curved upward. 
The periblematic cylinder follows the epidermis, and is easily distinguished from the 
latter on the one hand and the plerome derivatives on the other. The primary cortex, 
excepting the starch-ring, is made up of from three to seven layers of cells, which are 
prismatic, varying from 70-160 uw in height, and in cross section have a diameter varying 
from 5-40 uw, appearing irregular and rather angular or vermiform and near the epidermis 
are placed with their long axes radial, while further in they lie in the normal position. 
The starch-ring is conspicuous in both cross and long section. It consists normally of one 
layer of cells, but between the bundles it often increases to a thickness of three; the cells 
are cylindric or prismatic, having a diameter of from 10-60 uw and a height ranging from 
70-150 uw, and are strikingly larger than the neighboring elements of the primary cortex. 
The pleromatic cylinder has all its parts well developed. The stereome is composed 
of prismatic stereids, with rounded angles in cross section, forming a sheath one to four 
cells deep. The cells are from 10-40 w in diameter and 200-300 w high. The eylinder 
is continuous and most compact at the outside of the bundles, while between the latter 
the cells are larger and not as closely packed, and as is the case in section Bistorta, the 
septa are almost invariably transverse. The phloem is conspicuous as narrow fascicles 
toward the outer sides of the bundles. Between the latter it is interrupted for short 
distances by the intrusion of the stereome cylinder. The sieve-tubes and cells of the 
phloem are prismatic and in cross section appear quite angular, measuring from 5-10 « 
in diameter; in favorable sections they are distinct and vary in length from 100-160 w. 
The woody fibres in cross section are either square or oblong, and lie with their short axes 
radial. ‘They are smallest and most compactly arranged at the centers of the bundles, 
and range from 5-10 w in diameter. The ends are either oblique or tapering. As in 
the preceding subgenus, the tracheides and vessels occur normally along a line on either 
side of which the woody fibres and protoxylem are respectively situated. These large 
elements of the tracheae measure from 50-70 w in diameter and are either nearly circular 
in cross section or somewhat prismatic. In long section various combinations of the 
tracheides and vessels are found. Four different kinds are sometimes met with as repre- 
