THE LEAF.SHEATHS. 13 
It would seem that during the period characterised by great morphologieal 
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 differences in the character 
of the spinosity, of what we way 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 C. ornatus var. horridus is formidably beset 
with very large spines, while its VAR. mitis is almost smooth. 
The tubular 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 
removeable furfuraceous whitish-grey, or brown skin of fluffy indumentum, I know 
_ only C. tomentosus 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 ©. latifolius, C. marmoratus, 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 fibro-vascular 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 longitudi- 
nally raised ridge which terminates at the insertion of a spadix, or of a leaf-sheath 
flagellum, 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 
C. azillaris, where the leaf-sheaths are comparatively short and where one sheath 
covers 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 less open on the ventral 
side, as in C, erectus, so that they closely resemble the sheathing base of the fronds of — 
those Palms that have axillary spadices, the spadices of Calamus 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 split longitudinally | 
afterwards and the gap kept — by the growing central shoot. RO 
vna 
