Page 193 - Pharmacognosy 2 PG303

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

xylem vessels and tapering towards the cork on the outside. Below the cork, small
yellowish points are just visible and are due to the presence of sclereids in the
phelloderm. When the transverse surface is treated with sulphuric acid, 66 %, the
yellowish vessels and sclereids change to a deep green color.

Microscopical Characters
The vessels of the rays of secondary xylem are isolated or in radial rows

of 2-4 or in small groups of 2-8, they are about 65-150 µ in diameter and bear
transversely elongated pits or are reticulate. Surrounding the vessels is a little
lignified parenchyma, the cells having simple rounded pits, and a few fibrous
tracheids which are often irregularly curved, about 270-400 µ long and 12-43 µ
wide, and have pitted walls. The sieve tissue of the phloem collapses to form
patches of ceratenchyma. The parenchymatous medullary rays are from 6-15 or
more cells wide, and together with other parenchyma are filled with starch grains
which are rounded, ellipsoidal or irregularly ovoid, usually simple, sometimes 2-
3 compound, individual grains being 6-25-40-90µ in diameter, the hilum is
eccentric and may be a point or 2-4 radiate. The sclereids of the phelloderm are
sub-rectangular, about 40-110µ long and 20-50µ wide, with the walls perforated
by simple pits and having the radial and inner walls more strongly thickened than
the outer walls. Many of the sclereids contain from 1-6 prisms of calcium oxalate
measuring from 10-30µ.

Calumba Root: A, transverse surface of a slice; E,T. surface of a slice
of Coscinium stem; C,detailed T.S. of root. c, cambium; m.r , medullary
ray; p, pith; ph, phloem; s.t, sieve tissue; wp, wood parenchyma; xy,
xylem.

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