The leaves of palms are arranged either at more or less distant intervals along the stem, as in the canes (Calamus, Daemonorops) or are approximated in tufts at the end of the stem, thus forming those noble crowns of foliage which are so closely associated with the general idea of a palm. In the young condition, while still unfolded, these leaves form "the cabbage," in some species highly esteemed for food.
The adult leaf generally presents a sheathing base tapering up wards into the stalk or petiole, and this again bears the lamina or blade. The sheath and the petiole often bear stout spines, as in the rattan palms; and when, in course of time, the upper parts of the leaf decay and fall off, the base of the leaf-stalk and sheath often remain, either entirely or in their fibrous portions only, which latter constitute the investment to the stem already mentioned. In size the leaves vary within very wide limits, some being only a few inches in extent, while those of the noble Corypha may be measured in tens of feet. In form the leaves of palms are rarely simple ; usually they are more or less divided, sometimes, as in Caryota, extremely so. Usually the leaves branch regularly in a palmate fashion as in the fan-palms Latania, Borassus, Chamae raps, Sabal, etc., or in a pinnate fashion as in the feather-palms, Areca, Kentia, Calamus, Daemonorops (fig. 2), etc. The form of the segments is generally more or less linear, but a very distinct appearance is given by the broad wedge-shaped leaflets of such palms as Caryota and Martinezia. These forms run one into an other by transitional gradations; and even in the same palm the form of the leaf is often very unlike at different stages of its growth. The leaves are sometimes invested with hairs or spines; and, in some cases the under-surface is of a glaucous white or bluish colour, from a coating of wax.
The inflorescence of palms consists generally of a more or less fleshy spike, either simple or much branched, studded with numerous, sometimes extremely numerous, flowers, and enveloped by one or more sheathing bracts called "spathes." These parts coconut, Cocos nucif era, where the fibrous central portion invest ing the hard shell corresponds to the fleshy portion of a plum or cherry, while the shell or nut corresponds to the stone of stone fruits, the seed being the kernel.
The seeds show a corresponding variety in size and shape, but always consist of a mass of endosperm, in which is embedded a relatively very minute embryo. The hard stone of the date is the endosperm, the white oily flesh of the coconut is the same sub stance in a softer condition ; the so-called "vegetable ivory" is derived from the endosperm of Phytelephas.
The family contains upwards of 17o genera with probably about 1,500 species mainly tropical, but with some representatives in warm temperate regions. Chamaerops humilis is a native of the Mediterranean region, and the date-palm yields fruit in southern Europe as far north as 38° N. latitude. In eastern Asia the palms, like other tropical families, extend along the coast reaching Korea and the south of Japan. In America a few small genera occur in the southern United States and California; and in South America the southern limit is reached in Jubaea spectabile (the Chile coco nut) at 37° S. latitude. The great centres of distribution are tropical America and tropical Asia; tropical Africa contains only about a dozen genera, though some of the species, like the doum palm (Hyphaene thebaica) and the deleb or palmyra palm (Boras may be small, or they may attain relatively enormous dimensions, hanging down from amid the crown of foliage, or under the crown, like huge tresses, and adding greatly to the effect of the leaves. In some cases, as in the Talipot palm, the tree flowers only once, develops a huge inflorescence, and after the fruit has ripened, dies.
The individual flowers are usually small, greenish and insignifi cant in appearance; their general structure has been mentioned already. Modifications from the typical structure arise from dif ference of texture, and specially from suppression of parts, in con sequence of which the flowers are often unisexual, though the flowers of the two sexes are generally produced on the same tree (monoecious), not indeed always in the same season, for a tree in one year may produce male flowers and in the next female flowers. In a few cases they are dioecious. Sometimes the flowers are modified by an increase in the number of parts; thus the usually six stamens may be represented by 12 to 24 or even by hundreds. There are usually three carpels, more or less combined.