The genus Cinnamomum

1 2
Botany and Crop Improvement of Cinnamon and Cassia 29
Figure 2.4 Sketches showing two types of venation patterns. 1. A representative leaf of cinnamon
showing the typical acrodromous venation pattern. 2. A leaf of camphor tree showing the
acrodromous and pinnate-brochydodromous type of venation.
Shylaja (1984) also reported acrodromous venation pattern in south Indian species of
Cinnamomum. Baruah and Nath (1998) recognised three venation patterns in the
Cinnamomum species they have studied. In the majority of taxa venation pattern is
acrodromous. Here leaves are triplinerved, running in a convergent arch along with two
or rarely four lateral nerves. The lateral nerves in most taxa do not reach the apex. In
certain species (C. glanduliferum and C. glaucacens) venation is pinnate-camptodromous
(brachidodromous). In C. camphora and C. parthenoxylon venation is intermediate
between the above two patterns (Fig. 2.4).
The 1° veins are moderately stout and straight in C. malabatrum, C. cassia
and C. tamala. Lateral 1° veins are generally basal or supra basal. In the case of
C. camphora and C. parthenoxylon 1° veins are anastomosing with the secondaries.
In most cases the 2° veins arise from both sides of the 1° veins in an opposite or
sub-opposite manner and they are upturned and gradually disappear at apical
and basal margins. In C. camphora, C. glanduliferum and C. parthenoxylon 2° veins
arise on both sides of 1° veins in an alternate or sub-opposite manner and extend
towards the margins and join to form a series of prominent arches (Baruah and Nath,
1998).
The number of 2° veins varies from leaves to leaves in a single taxon, as does the angle
between 1° and 2° veins. In C. cassia, C. glanduliferum, C. glaucacens, and C. parthenoxylon
the sub-adjacent 2° arches are enclosed by 3°–4° arches, while these 2° arches are
simple in other taxa studied by Baruah and Nath (1998).
Minor veins of the 4° and 5° order, which originate from 3° veins, constitute the
areoles or vein islets. The areoles are generally tetragonal or polygonal in shape. The size
and number of areoles are variable in apical, middle and basal portions of lamina.
Veinlet endings are generally simple (linear or curved).