Page 256 - Pharmacognosy 2 PG303

Pharmacognosy-2 (PG303) Level 2 Clinical Pharmacy-Pharm D

xylem; 3. T. S and diagram; a, cork; b, phelloderm; c, cambium;
d, xylem; e, starchy medullary rays; f, wood part; g, cortex.

The root occurs in nearly cylindrical or slightly tapering, straight slightly
wavy, or flexuous pieces. They vary in length up to 60 cm long and up to 1.5 cm in
diameter: sometimes with a thick knotty crown, about 5 cm long and up to 3 cm
thick, having several heads and giving numerous root branches. Externally, it is
light reddish brown to deep brownish red, somewhat longitudinally wrinkled,
rugged and scaly in the old, almost smooth in the young pieces, but no
transverse cracks (distinction from Para Rhatany). Fracture is shortly fibrous in
the bark, tough and splintery in the wood. Internally, it consists of bright reddish-
brown bark, occupying up to about one-third of the radius of the root
(distinction from Para Rhatany) and somewhat loosely adhering to yellowish or
pale reddish-brown, dense, hard, finely radiate wood, commonly with a small central
darker heartwood in the old pieces but no annual rings.

Microscopical Characters
Cork is formed of numerous layers of thin walled, polygonal tabular cells with
reddish-brown contents. Cortex consists of phelloderm, narrow, of somewhat
thick-walled cells. Phloem constitutes the main part of the bark, traversed by
numerous 1-cell wide medullary rays and containing numerous slender fibers. The
latter are about 12-30 µ in diameter and 400-1000 µ in length, with somewhat wide
lumen, thick non-lignified walls and irregular outline, singly or in groups of
variable size, radially arranged, frequently accompanied by cells containing
prismatic or micro-crystals of calcium oxalate. Xylem is diffused, porous, mainly
formed of spindle-shaped, narrow lignified, thick-walled fibers, traversed by
numerous 1-cell wide medullary rays and few diffused parenchyma cells in
tangential bands and numerous vessels. The vessels are isolated or occasionally in
groups of 2-5, each 20-65 µ wide and about 120-300 u long, with bordered pits, in
longitudinal, often rather distant rows. Both phloem and wood parenchyma contain
starch granules and reddish-brown coloring matter, present also in cork cells, and
in some bast and wood fibers.

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