Page 250 - Pharmacognosy 2 PG303

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

in nearly cylindrical pieces, entire or longitudinally split, 3-20 cm long, 0.5-2.5
cm rarely up to 4 cm thick, occasionally reaching 4-8 cm at the crown. Externally,
it is yellowish brown to dark brown. The root is longitudinally wrinkled and
furrowed, sometimes twisted with a few scars of lateral rootlets. Rhizome is erect,
with numerous transverse annulations of encircling leaf scars, occasional scars of
rootlets, frequently terminates in a bud and occasionally branched. Fracture is
short when dry but tough and flexible when moist. Internally, it is reddish
yellow, showing a somewhat yellowish- to reddish-brown bark, a well-marked,
dark, wavy cambium ring and a large yellowish brown parenchymatous xylem. Pith
is central, present only in rhizome.

Microscopical Characters
Cork is yellowish-brown, formed of few layers of polygonal tabular cells,

with slightly wavy walls. Cortex consists of phelloderm in root, of several layers;
the outer collenchymatous with thick-walled cells, sometimes contain oily
globules and minute acicular crystals of Ca OX. The inner consists of tangentially
elongated parenchyma, the cells being more or less collapsed and separated by
large inter-cellular spaces, and each containing a distinct nucleus and minute
needle shaped crystals of Ca OX. Phloem consists of polygonal parenchyma and
numerous scattered groups of thin-walled sieve tubes with companion cells. Xylem
is formed principally of thin-walled parenchyma, containing minute crystals of Ca
OX and oil globules. Vessels are large slightly lignified, reticulate or scalariform,
scattered singly or in small groups, with a tendency to a radial arrangement near
the cambium, and small groups of collapsed tissue of interxylary phloem. Primary
xylem is 3-arch and may be found in the center. Medullary rays are parenchymatous
and not clearly marked. Pith, in rhizome only, is parenchymatous with anastomosing
vascular strands. Starch granules are rarely present in parenchyma, small, oval.

Gentiana lutea: A, piece of root. B, portion of vertical
rhizome; C, root cut transversely; D, rhizome cut transversely;

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