Page 198 - Pharmacognosy 2 PG303

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

Rauwolaia root. A, root of R. serpentina; B,T.C. of same;
C,diagramnatic T.S.; D,T.S. of cork; E,T.S: of secondary
wood; F, fibres and vessel. ck, cork; f, fibre; g.r, growth ring; m.r,
medullary ray; pd, phelloderm; ph, phloem; r, resinous material;
s,starch; sc, group of sclereids; v, vessel; xy, xylem .

Microscopical Characters
Externally the root is covered by a stratified cork with about 2-7 alternating

bands of smaller cells in I-7 layers and of larger cells in 1-3 layers; the cork cells
are isodiametric in surface view, about 18-35-56µ longitudinally and 49-56-70µ
tangentially; radially the smaller cells measure about 5-15µ and the larger ones 40-
100µ; all the cork cells are suberized, but the larger cells only are also lignified, the
phelloderm is composed of about 10-12 rows of cellulosic parenchyma. The
phloem, as seen in a transverse section, consists of narrow rays of sieve tissue and
parenchyma which alternate with broader medullary rays composed of large cells
and usually 2-4 cells wide; many cells of the phloem parenchyma contain calcium
oxalate in conglomerate crystals with a few well formed prisms and occasional cells
are filled with a granular secretion staining yellow with iodine, the remaining
parenchyma contains starch granules. The xylem has a dense central tetrarch core,
about 0.5 mm. wide containing many small vessels, the remainder of the secondary
wood contains much parenchyma with small groups of' fibers and narrow vessels
about 35-54µ in diameter numerous large-celled medullary rays; the parenchyma of

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