Page 199 - Pharmacognosy 2 PG303 (1)

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

both xylem and medullary rays is lignified, the cells have numerous circular pits in
their walls and contain small starch granules; the secondary xylem has well-marked
annual rings. The starch granules are mostly simple and rounded, occasional
granules are 2- to 3-compound; they are rapidly gelatinized by cold 0.9 % aqueous
solution of potassium hydroxide; they show a well-marked cross by polarized light
and they measure about 4-20-50 µ in diameter.

The tissues of the rhizome have characters similar to those of the root; there
is in addition a cortex, a pericycle with unlignified pericyclic fibers and small pith.
Many of the thick-walled pericyclic fibers have an elongated ovoid enlargement
near the end, a feature which is typical of the Apocynaceae. In the periphery of the
pith there are about 20 small strands of perimedullary phloem. Stone cells are absent
from both rhizome and root.

Rauwolfia serpentina Benth., Rhizoma. A. diagrammatic
transverse section., c. cambium; ck, cork; cl, cortex; f, xylem
fiber; p, pith; pd, phelloderm; p.f., pericyclic fiber; p.f.l., tip of
pericyclic fiber showing local enlargment; ph. Phloem; p.ph.
perimedullary phloem; r, growth ring; s.c., secretion cell; st, sieve
tissue; v, vessel; xy, xylem.

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