12 INTBOEUCTOBT ESSAY.
Very commonly we find the central costa and some of the lateral primary
nerves more or less beset, now on the upper, now on the lower surface and now
on both with hairs, bristles or spinules; the presence or absence or varied situation
of these supply easy though not always reKable differential characters. In 0. cilmris
and in other species of the same group the secondary and tertiary nerves are also
covered with haii-s, and if these nerves be numerous and very close together,
the surface has the appearance of being uniformly hairy, as for example in
C. Iiispidulvs.
In a very few species a solitary spine is found, though not constantly, on the
upper sm-lace of the central costa near the base oi the leaflet (0. tenuis and 0. Rotang),
In C, 3j)imfoltuji the leaflets are armed with 3-5 erect and comparatively strong true
spines. The leaflets of C. salidfolius are also more or less supplied with a few spines
of this character ; these, however, are absent from its var. Iciophyllus.
In texture the leaflets of Calamus are usually thinish, sonietimes sub-herbaceous
or membraiious, often cbartaceous, and occasionally thinly coriaceous; very
frequently both surfaces are of the same green colour, but the upper sui-face is
most usually shining while the lower is dull. In comparatively few species the
lower surface is more or less conspicuously different in colour, being mealy-pulverulent
and subpuipurescent in 0. Griffithu^ glaacescent in 0. cmitts, mealy-ochi-aceous
in C. sijmjihljsipus^ mealy-white in C. arborescens and C. hypoleMus, or decidedly
white and as if coated with a thin chalky layer in 0. Lobbiams, 0. Uimies and
G diseolor. Only in 0. deerratus have I observed the lower surface sprinkled with
small punctiform scales.
The margins of the leaflets of Calami are very seldom absolutely smooth;
commonly they are furnished with cilia or very small
spinules.
The leaves of Calami usually retain their light green colour in dried specimens,
but certain species, especially those of the 0. andamanious and of the C.
groups, assume in drying a light brown or tobacco colour, while ft
C. Martianus, C. insianis and a few others
specimens by their bright yellow hue.
readily recognisable in herbarium
v.—The Leaf-Sheiitlin.
The leaf-sheaths of the leaves of Calamus are very important organs of the
plant. In most Calam, in all those species we may say that are scandcnt, a leafsheath
arises from^^each ring of the stem and forms a complete more or less elongated
cyliadric tube round the internode immediately above. In the non-scandent species
the leaf-sbeaths are more or less open along the ventral aspect.
The leaf-sheaths are always of a firm, tough or more or less coriaceous texture,
and are sometimes even woody; but their leading characteristic is that they are
always morel or less covered with spines, which assume a great variety of forms and
furnish one of the most conspicuous and useful diagnostic characters for the discrimination
of many species.
THE LEAF.SHEATHS. 13
It would seem that during the period characterised by great morphological
malleability of organisms the tendency to variation was very active in the direction
of acquiring a high degree of spinosity, as being that which secured for the
plants its most valuable means of defence. But while diflerences in the character
of the spinosity, of what we may call the "armature" of the leaf-sheaths, afford one
of the best characters in distinguishing the species of Calamus, it sometimes happens
that two plants one with powerfully armed the other with smooth leaf-sheaths, cannot
be considered specifically distinct; thus O. arnatus VA». lurridm is formidably beset
with very large spines, while its VAE. mitis is almost smooth.
The tubiJar cylindric leaf-sheaths have commonly a kind of pouch in their dorsal
upper portion at the base of the petiole, so that they may be termed gibbous ; the
leaf-sheaths of the non-scandent species which are open on the ventral side are
without this peculiarity and are gradually narrowed into the petiole.
Leaving the spines out of account the surface of the leaf-sheath is at times
glabrous, pulverulent, greenish, glaucous, or more or less clothed with a deciduous or easily
lemoveable furfnraceous whitish-grey, or brown skin of flufly indumentum. I know
only C. tommiosus where the sheaths, in common with other parts of the plant, are
entirely clothed with a permanent white tomentum.
The leaf-sheaths are often longitudinally striate or indented with the impressions
stamped upon them by their own spines.
In a few species, such as G. luiifolius, C. inarmoratus, C. Feanus, C. javensis, the
sheaths in the younger parts of the plant are variegated, spotted or marbled with
whitish, dark-green or purplish patches.
The fact that the most important flbro-vasculaj.- bundles, such as those that enter
the reproductive organs, pass from the stem through the nodes into the sheaths
indicates the complex, almost sympodial character of this part of the leaf. The
vascular bundles usually traverse the entire length of the sheaths, and their surface is
generally marked externally, as has already been seen, by a more or less longitudinally
raised ridge which terminates at the insertion of a spadiz, or of a Icaf-sheath
fiagellnm, laterally near the mouth of the leaf-sheath itself.
Owing to this peculiarity of structure the spadices, like the flagella, emerge from
near the apex of the sheaths and never arise in the axils of the fronds; only in
0. azillaris, where the leaf-sheaths are comparatively short and where one sheath
COTers a considerable portion of that immediately above, do the spadices, which
moreover are inserted far below the mouth of the sheaths, appear axillary. Even
when the sheaths are not exactly tubular but are more or lass open on the ventral
side, as in G. ereclm, so that they closely resemble the sheathing base of the fronds of
those Palms that have axillary spadices, the spadices of Oalamm retain their usual
position and emerge laterally from near the apex of their proper sheaths; so that
it appears as if the sheath at first formed a closed tube but was spKt longitudinally
afterwards and the gap kept open by the growing central shoot.