PALMAE 
499 
is familiar — a crown of leaves at the end of an unbranched stem 
(Hyphaene is branched). The stem exhibits various forms; some 
palms, eg. Nipa, Phytelephas, have a short stock bearing ‘radical’ 
leaves; some, e.g. Geonoma, Calamus, Desmoncus, have a thin reed- 
like stem with long internodes (the two latter genera are climbers); 
others again have a tall stem with a crown of leaves at the top. The 
stem is often covered with the remains of old leaf-sheaths, or is 
thorny. Its height reaches 150 feet in some sp., and it grows slowly 
in thickness, by a method which requires investigation. At the base 
the stem is usually conically thickened or else provided with buttress 
roots; this gives the necessary mechanical rigidity and is a con- 
sequence of the fact that the stem does not curve in a gale but bends 
from the base, from a position like | to one like f. The stems of 
Cocos and other palms are curved instead of straight ; the meaning of 
this is unknown. 
The leaf is very characteristic ; the only closely similar leaf is that 
of Carludovica, though those of Cycads and some tree ferns have a 
superficial likeness to palm-leaves. Some genera have palmate (fan) 
leaves, some pinnate (feather) leaves, but this structure arises by a 
development unlike that which gives rise to these forms in Dicoty- 
ledons and more like that which occurs in Araceae (see Nat. PJll). 
The leaf is usually very large, and at the base of the petiole is a 
sheath, which makes a firmer attachment to the stem than a mere 
articulation. The sheath contains many bundles of fibres, which 
remain after the decay of the softer tissues. The pinnae are folded 
where they meet the main stalk of the leaf, sometimes upwards 
{induplicate, V in section), sometimes downwards ( reduplicate , /\ in 
section) ; these characters are important in classification. The leaf 
emerges from the bud in an almost vertical line and thus, placing its 
apex to the sky, escapes excessive radiation and transpiration. The 
palms are pronounced sun-plants (p. 142), and show xerophytic cha- 
racters in their leaves. The leaf-surface is glossy with a thick cuticle, 
and is rarely arranged perpendicularly to the incident rays. Often 
the leaf is corrugated, or placed at an angle by the twisting of the 
stalk or by the upward slope of the stalk ; sometimes the leaflets slope 
upwards, and so on. 
The infl. is usually very large and much branched. In Corypha 
and others it is terminal, its production being a mark of the end of 
the life of the plant (cf. Agave), but usually it is axillary; sometimes 
the infls. are in the axils of the current leaves, sometimes lower on 
the stem. The branching is racemose and the firs, are often em- 
bedded in the axis, so that the whole is often termed a spadix. It is 
enclosed in a spathe of several leaves and emerges from it when the 
firs, are ready to open. Some Palms are dioecious, some monoecious, 
in the latter case often with the firs, in groups (small dichasia) of 3, 
one $ between two S . 
32—2 
