WHO monographs on selected medicinal plants - travolekar.ru

<strong>WHO</strong> <strong>monographs</strong> on selected medicinal plants
viewed in cross-section, the secondary cortex is characterized by large
subspherical groups of yellow sclereids and radially oriented medullary
rays which are 1–2 cells broad. The parenchyma cells of the secondary
cortex contain calcium oxalate prisms (up to 20 μm in length) and oil
droplets. When viewed in longitudinal section, the sclereid aggregates are
unusually long. The calcium oxalate crystals are arranged in longitudinal
rows. Starch granules are infrequent, but when present, they are subspherical
(2–6 μm in diameter). Scattered through the cortex are groups of
stone cells and occasional isolated stone cells. Rifts or spaces of natural
origin also occur in this region. Pericycle consists of parenchyma similar
to the cortex, embedded with a few pericyclic fibres. The latter, when
observed in longitudinal sections, possess an irregular lumen and obtuse
or rounded ends. Phloem is of variable width, consisting of sieve tissue,
phloem parenchyma and phloem rays; the phloem parenchyma contains
starch grains, rosette aggregates and monoclinic prisms of calcium oxalate,
tannin, amorphous orange, yellow or olive brown masses and oil.
The phloem rays vary from straight to slightly curved or wavy and, while
mostly 1 to 2 cells in width, may be up to 3 cells in width, as best determined
from tangential-longitudinal sections through this region of the
bark. Scattered through the phloem are numerous groups of stone cells.
The margins of these groups are irregularly rounded, crenate, toothed and
indented. Some of the phloem rays are intercepted in their outward course
by groups of stone cells. As the stems grow older, secondary cork cambia
originate successively in the cortex, pericycle and outer phloem forming
wavy borke areas in these zones which contain groups of stone cells and,
in the case of the pericyclic region, pericyclic fibres. In old stem bark, the
medullary rays (phloem rays) reach outward to the periderm (3, 6).
Root bark: cork of variable thickness, composed of somewhat lignified
cork cells which are tangentially elongated in cross-sections and polygonal
in surface sections, many of which possess orange or yellowish-orange or
brownish contents. Phellogen of tangentially elongated meristematic cells.
A secondary cortex of a narrow zone of tangentially elongated parenchyma
cells, some of which contain orange or brownish amorphous masses,
tannin, oil globules, starch, monoclinic prisms and rosette aggregates of
calcium oxalate. Groups of stone cells with irregularly indented margins
and isolated stone cells scattered through the region. Phloem consists of a
relatively broad zone comprising a matrix of parenchyma and sieve tubes
separated into a number of oblong or curved phloem patches by medullary
rays which, in cross-sections, run nearly straight or curve and converge
in groups. The stone cell groups are numerous and frequently deeply
notched, the individual stone cells are strongly lignified with prominent
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