Page:Encyclopædia Britannica, Ninth Edition, v. 18.djvu/208

190 PALM its overthrow by the wind. The underground stem of some species, e.g., of Calamus, is a rhizome, or root-stock, lengthen ing in a more or less horizontal manner by the development of the terminal bud, and sending up lateral branches like suckers from the root-stock, which form dense thickets of cane-like stems. The branching of the stem above ground is unusual, except in the case of the Doum Palm of Egypt (Hyph&ne), and, when present, is probably the result of some injury to the terminal bud at the top of the stem, in consequence of which buds sprout out from below the apex. The internal structure of the stem does not differ funda mentally from that of a typical monocotyledonous stem, the taller, harder trunks owing their hardness not only to the fibrous or woody skeleton but also to the fact that, as growth goes on, the originally soft cellular tissue through which the fibres run becomes hardened by the deposit of woody matter within the cells, so that ultimately the cellular portions become as hard as the woody fibrous matters proper. The leaves of palms are either arranged at more or less distant intervals along the stem, as in the canes (Calamus, <fcc.), 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, with the succulent end of the stem from which they arise, form " the cabbage," which in some species is highly esteemed as an article of food. The adult leaf very generally presents a sheathing base tapering upwards into the stalk or petiole, and this again bearing the lamina or blade. The sheath and the petiole are very often provided with stout spines ; 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 Caryota may be measured in tens of feet. In form the leaves of palms are very rarely simple ; usually they are more or less divided, sometimes, as in Caryota, extremely so. In Geonoma Verschaffeltia, and some others, the leaf splits into two divisions at the apex and not elsewhere ; but more usually the leaves branch regularly in a palmate fashion as in the fan-palms Latania, Chamxrops, Sabal, &c., or in a pinnate fashion as in Areca, Kentia, Calamus, &c. 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, Martinezia, or Mauritia. These forms run one into another by transitional gradations ; and even in the same palm the form of the leaf is often very different at different stages of its growth, so that it is a difficult matter to name correctly seedling or juvenile palms in the condition in which we generally meet with them in the nurseries, or even to foresee what the future development of the plant is likely to be. Like the other parts of the plant, the leaves are sometimes invested with hairs or spines; and, in some instances, as in the magnificent Ceroxylon andicola, the under surface is of a glaucous white or bluish colour. The inflorescence of palms consists generally of a fleshy spike like that of an Arum, either simple or much branched, studded with numerous, sometimes extremely numerous, flowers, and enveloped by one or more sheathing bracts called " spathes." These parts may be small, or they may attain relatively enormous dimensions, hanging down from amid the crown of foliage like huge tresses, and adding greatly to the noble effect of the leaves. As to the individual flowers, they are usually small, greenish, and insignificant; their general structure has been mentioned already. Modifications from the typical struc ture arise from differences of texture, and specially from suppression of parts, in consequence of which the flowers are very generally unisexual (figs. 1, 2), 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 all male flowers and in the next all female flowers. Sometimes the flowers are modi fied by an increase in the number of parts ; thus the usually six stamens may be represented by 12 to 24 or even by hundreds. The carpels are usually three in number, and more or less combined ; but they may be free, and their number may be reduced to two or even one. In any case each carpel contains but a single ovule. Owing to the sexual arrangements before mentioned, the pollen has to be transported by the agency cf the wind or of insects to the female flowers. This is facilitated some times by the elastic movements of the stamens and anthers, which liberate the pollen so freely at certain times that travellers speak of the date-palms of Egypt (Phoenix dactyl if era] being at daybreak hidden in a mist of pollen grains. In other cases fertilization is effected by the agency of man, who removes the male flowers and scatters the pollen over the fruit-bearing trees. This practice has been followed from time immemorial ; and it afforded one of the earliest and most irrefragable proofs by means of which the sexuality of plants was finally established. The fruit which results from this process of fertilization is various: sometimes, as in the common date, it is a berry with a fleshy rind enclosing a hard stony kernel, the true seed; sometimes it is a kind of drupe as in the cocoa-nut, Cocos nucifera, where the fibrous central portion investing 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. Sometimes, as in the species of Sagus, Raphia, etc., the fruit is covered with hard, pointed, reflexed shining scales, which give it a very remarkable appearance. The seed varies in size, but always consists of a mass of perisperm, in which is imbedded a relatively very minute embryo (fig. 3). The hard stone of the date is the perisperm, the white flesh of the cocoa-nut is the same substance in a softer condition; the so-called " vegetable ivory ); is derived from the perisperm of Phytelephas. Hooker, who in his recent revision of the genera follows the work of his predecessors Martius, Wendland, and Drude, enumerates about one hundred and thirty-two genera of the order ranged under five tribes, distinguished by the nature of the foliage, the sexual conditions of the flower, the seed umbilicate or not, the position of the raphe, etc. Other characters serving to distinguish the minor groups are afforded by the habit, the position of the spathes, the " aestivation " of the flower, the nature of the stigma, the ovary, fruit, &c. It is impossible to overestimate the utility of palms. They furnish food, shelter, clothing, timber, fuel, building materials, sticks, fibre, paper, starch, sugar, oil, wax, wine, tannin, dyeing materials, resin, and a host of minor pro ducts, which render them most valuable to the natives and to tropical agriculturists. The Cocoa-nut Palm, Cocos nuci- fera, and the Date Palm, Phcenix dactylifera, have been treated under separate headings. Sugar and liquids capable of becoming fermented are produced by Caryota urens, Cocos nucifera, Borassus flabelliformis, Rhapis vim/era., Arenga saccharifera., Phoenix xilvestris, Mauritia vinifera, &c. Starch is procured in abundance from the stem of the Sago Palm, Sagus Rumphii, and other species. The seeds of Elais guineensis of western tropical Africa yield, when