PALM, originally the flat of the hand, in which sense it is still used ; from this sense the word was transferred as a name of the trees described below. The emblematic use of the word ( =prize, honour) represents a further transference from the employment of the palm-leaves as symbols of victory.
The palms, botanically Palmae or Palmaceae, have been termed the princes of the vegetable kingdom. Neither the anatomy of their stems nor the conformation of their flowers, however, entitles them to such position, but in general character they are noble plants. Their stems are not more complicated in structure than those of the common butcher's broom (Ruscus) ; their flowers are for the most part as simple as those of a rush (.luncus). The family Palmaceae is characterized among monocotyledonous plants by the presence, for the most part, of an unbranched stem bearing a tuft of leaves at the extremity only, or with the leaves scattered; these leaves, often gigantic in size, are usually firm in texture and branching in a pinnate or palmate fashion. The flowers are borne on simple or branching spikes, very generally protected by a spathe or spathes, and each consists typically of a perianth of six greenish somewhat inconspicuous segments in two rows, with six stamens, or pistil of one to three carpels, each with a single ovule and a succulent or dry fruit, never dehiscent. The seed consists almost exclusively of endosperm or albumen in a cavity in which is lodged the relatively very minute embryo. Some of the more important modifications may be noticed briefly.
Taking the stem first, it is in very many palms relatively tall, erect, unbranched, regularly cy lindrical, or dilated below so as to form an elongated cone, either smooth, or covered with the pro jecting remnants of the former leaves, or marked with circular scars indicating the position of those leaves which have now fallen away. It varies in diameter from the thickness of a reed (as in Chamaedorea) to a sturdy pillar-like structure as seen in the date-palm, Palmyra palm or Talipot. In other cases the very slen der stem is prostrate, or scandent by means of formidable hooked prickles which, by enabling the plant to support itself on the branches of neighbouring trees, also permit the stem to grow to a very great length and so to expose the foliage to the light and air above the tree-tops of the dense forests, as in the genus Calamus, the rattan or cane palms (see LIANES). In some examples the
trunk, or that portion of it above ground, is so short that the plant is in a loose way called "stemless," as in some kinds of the Sabal tribe, and as happens sometimes in the only species found in a wild state in Europe, Chamaerops humilis. The vegetable ivory (Phytelephas) of equatorial America has a very short thick stem bearing a tall cluster of leaves which appears to rise from the ground. In many species the trunk is covered with a dense net work of stiff fibres, often compacted together at the free ends into spines. This material, which is so valuable for cordage, consists of the fibrous tissue of the leaf-stalk, which in these cases persists after the decay of the softer por tions. It is very characteristic of some palms to produce from the base of the stem a series of ad ventitious roots which gradually thrust themselves into the soil and serve as buttresses to steady the tree and prevent its over throw by the wind. The under ground stem of some species, e.g., of Calamus, is a rhizome, or root stock, lengthening in a more or less horizontal manner by the de velopment 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 un usual; however, in the Doum palm of Egypt (Hyphaene), the stem forks, often repeatedly ; this is due to the development of a branch to an equal strength with the main stem.
The internal structure of the stem does not differ funda mentally from that of a typical monocotyledonous stem ; the taller, harder trunks owe their hard ness 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 the cellular portions become as hard as the woody fibrous tissue.