Monographs Details: Rhizophora mangle L.
Authority: Britton, Nathaniel L. Flora Borinqueña.
Description:Species Description - Mangle is an aboriginal name for this common tropical tree, anglicized into Mangrove. It is one of the most highly specialized of all trees, inhabitating only quiet, shallow, salt water, and forming nearly impenetrable thickets by its density of growth, its numerous, stout, aerial roots (Rhizophora is Greek, meaning root-bearing), and the greatly elongated radicles of the embryo of the seeds, which may reach the mud before the fruit falls; it is distributed throughout tropical America, extending north to Florida and to Bermuda, is locally abundant in Porto Rico and grows also in tropical Africa. Whether its original area of development is American or African may only be conjectured; the impossibility of parallel development yielding such an identical, complex organism on both sides of the Atlantic Ocean must be admitted; we must conclude that at some remote period, probably antedating the human era, there was a transferral of living material from one coast to the other; this might have been through floating, for the plant can, doubtless, retain vitality in salt water, indefinitely; we may further suspect that the movement was from Africa to America, invoking the agency of east to west trade winds, and the known existence of two other species of Rhizophora in the Old World tropics. We dismiss the theory of ancient land connection through the Atlantic tropics as fanciful.
Rhizophora Mangle may form a tree 10 meters high, or higher, but is usually much lower and often shrubby; the bark is astringent and used for tanning; the stout, smooth twigs are pithy, the brown, strong, heavy wood valued for piles and for boat-building. The leathery, smooth, opposite, untoothed leaves are short-stalked, elliptic, blunt, from 5 to 15 centimeters long, with a stout midrib; the large stipules, to be seen on young twigs, fall away early. The flowers are borne 2 or 3 together on a forked stalk; they have a short top-shaped or bell-shaped calyx-tube, and 4, leathery, narrow, recurved sepals about 10 millimeters long; there are 4, narrow, pale yellow petals which are cobwebby, and 2-cleft at the tip; the 4 to 12 stamens are short; the ovary is 2-celled, with 2 ovules in each cavity, the stigma 2-lobed. The leathery fruit is 2 or 3 centimeters long, pendulous, the solitary seed germinating within it, the radicle protruding.
Rhizophora Mangle Linnaeus, Species Plantarum 443. 1753.