The genus Cinnamomum

Botany and Crop Improvement of Cinnamon and Cassia 35
characteristic features of Cinnamomum barks. The distance between such groups is more
in C. camphora (mean 0.621 mm), while it is lesser in C. malabatrum (mean 0.137 mm).
The distribution of bast fibres is another characteristic feature of the barks. In C. cassia
and C. verum such fibres are rare and sparsely distributed. In C. camphora they are
frequent, while in C. malabatrum they are very frequent.
The cortical region of young bark and the phellem and phelloderm regions of older
bark contain a large number of cells with brown tannic deposits. Such cells are frequent
in C. cassia and C. verum, and less frequent in C. camphora and C. malabatrum. Oil globules
are abundant in the outer bark tissues of C. cassia and C. verum, but are very few in
C. camphora and almost absent in C. malabatrum.
Crystalline inclusions, mostly in the form of raphides or prismatic crystals, occur in
the bark of all the species except in C. camphora. Raphides are distributed sparsely in
C. cassia and C. verum. They are abundant in C. malabatrum. Raphides are needle-shaped
or spindle-shaped, occurring alone or in groups in the phloem tissues.
Chaudhuri and Kayal (1971) made a detailed study on the barks of four species of
Cinnamomum (C. verum, C. camphora, C. tamala and C. iners). The following discussion is
based on the above authors.
In C. verum the bark is yellowish brown to brown, the outer surface either smooth or
rough, uneven, irregularly fissured and longitudinally striate showing circular or irregular
brownish patches occasionally with perforations that indicate the positions of
nodes. In commercial samples the outer surface is devoid of the suberous coat and often
some parts of the middle region. The middle region is granular due to the presence of
groups of stone cells; the inner surface is brownish to dark brownish in colour, smooth
and soft with faint striae.
Phellem or cork consists of five to ten layers of tangentially elongated, more or less
thin-walled, slightly suberised cells. In commercial samples these layers may be
completely absent. The cork cells adjacent to the cortex are thin-walled with the inner
tangential walls sclerosed.
The phellogen and phelloderm layers are not very distinct and the cortex is not
sharply defined from the pericyclic region. The cortex consists of thin-walled
parenchymatous cells, which are tangentially elongated and 10–16 layered in thickness.
Cortical parenchyma cells contain tannin. Many secretory cells containing oil
are intermingled with cortical parenchyma cells. Secretory cells measure 19–35
35–90 in T.S. Pericycle consists of a continuous ring of stone cells, three to four
cells in width, which are elongated tangentially, thick-walled and pitted. Inner cells
are thicker than the outer ones thereby giving a characteristic appearance. Pericycle
fibres occur at intervals and are lignified, elongated and taper at both ends. These
fibres measure 300–650 in length and 18–35 in breadth. The inner region of the
stone cell ring consists of six to ten layers of parenchymatous, thin-walled, tangentially
elongated cells, intermingled with oil cells and cells containing mucilage.
Phloem constitutes about 50% of the thickness of the bark and consists of sieve
tubes, phloem parenchyma, phloem fibres and medullary rays. Sieve tubes are
arranged in tangential bands, which are completely collapsed in the outer layer. Sieve
plates are on the transverse walls. Phloem parenchyma consists of sub-rectangular or
rounded cells, which are tangentially elongated and filled with starch grains and small
acicular crystals of calcium oxalate. Starch grains are simple as well as compound.
Phloem parenchyma cells contain tannin. Associated with the phloem parenchyma
are the phloem fibres, which are elongated tangentially, lignified, thick walled and