Trees, with pithy branchlets, thick astringent bark, and adventitious fleshy roots. Leaves ovate or elliptic, glabrous, petiolate; stipules elongated, acuminate, infolding the bud, caducous. Flowers perfect, yellow or creamy white, sessile or pedicellate, bibracteolate, the bractlets united into an involucral cup, in pedunculate dichotomously or trichotomously branched clusters, the base of their branches surrounded by an involucre of 2 ovate 3-lobed persistent bracts, or 1-flowered; calyx 4-lobed, the lobes acute, coriaceous, ribbed on the inner surface and thickened on the margins, two or three times longer than the turbinate globose tube, reflexed at maturity, persistent; petals 4, induplicate in the bud, alternate with and longer than the calyx-lobes, inserted on a fleshy disk-like ring in the mouth of the calyx-tube, involute on the margins, coated on the inner surface with long pale hairs, or flat and naked, caducous; stamens 8—12; filaments short or 0; anthers attached at the base, introrse, elongated, connivent, areolate; ovary partly inferior, conic, 2-celled, contracted into two subulate spreading styles stigmatic at apex. Fruit a conic coriaceous berry surrounded by the reflexed calyx-lobes and perforated at the apex by the germinating embryo. Seed germinating in the fruit before falling, the apex surrounded by a thin albuminous cup-like aril; seed-coat thick and fleshy; embryo surrounded by a thin layer of albumen; cotyledons dark purple; radicle elongated, clavate, and when fully grown separating from the narrow exserted woody tube inclosing the plumule and developed from the cotyledons after the ripening of the fruit.
Rhizophora with three species is widely and generally distributed on the shores of tidal marshes in the tropical regions of the two hemispheres, one specie reaching those of southern Florida. It possesses astringent properties; the bark has been used in tanning leather, in dyeing, and as a febrifuge. The wood is hard, durable, and dark-colored. By means of the aerial germination of its seeds and in its power to develop roots from trunks and branches, Rhizophora is especially adapted to maintain itself on low tidal shores and is an important factor in protecting and extending them into the ocean. Roots springing from the stems at a considerable distance above the ground and arching outward descend into the water and fix themselves in the mud beneath, while roots growing down from the branches enter the ground and gradually thicken into stems. The fully grown radicle ready to put forth roots and leaves, and often 10′—12′ long, is thicker and heavier at the root end than at the other, and in detaching itself from the cotyledons and in falling the heavy end sticks in the mud, while the plumule at the other end, held above the shallow surface of the water, soon unfolds its leaves.
The generic name, from ῥίζα and φέρειν, was used by early authors to designate various climbing plants with thickened roots.
1. [Rhizophora Mangle] L.
Leaves ovate or elliptic, rounded or acute at apex, gradually narrowed at base, dark green and very lustrous on the upper surface, paler on the lower surface, 3½′—5′ long and 1′—2′ wide, with slightly thickened margins, a broad midrib, and reticulate veinlets; persistent for one or two years; petioles ½′—1½′ in length; stipules lanceolate, acute, 1½′ long, deciduous as the leaf unfolds. Flowers produced through the year, 1′ in diameter, pedicellate, in 2 or 3-flowered clusters on peduncles 1½′ long from the axils of young leaves; petals pale yellow, coated on the inner surface with long pale hairs; stamens 8 with villose filaments. Fruit 1′ long, rusty brown, slightly roughened by minute bosses, the hard woody thick-walled tube developed from the cotyledons protruding ½′—⅔′ from its apex after the germination of the seed, covering the plumule, and holding the dark brown radicle marked with occasional orange-colored lenticels and when fully grown 10′—12′ long and ¼′—⅓′ thick near the apex.
A round-topped bushy tree, with spreading branches usually 15°—20° high, forming almost impenetrable thickets with its numerous aerial roots, or occasionally 70°—80° high, with a tall straight trunk clear of branches for more than half its length, a narrow head, and stout glabrous dark red-brown branchlets, becoming lighter colored in their second year and then conspicuously marked by large oval slightly elevated leaf-scars. Bark of young stems and of the branches smooth, light reddish brown, becoming on old trunks ⅓′—½′ thick, and gray faintly tinged with red, the surface irregularly fissured and broken into thin appressed scales. Wood exceedingly heavy, hard, close-grained, strong, dark reddish brown streaked with lighter brown, with pale sapwood of 40—50 layers of annual growth; used for fuel and wharf-piles.
Distribution. Shores of Florida from Mosquito Inlet on the east coast and Cedar Keys on the west coast to the southern keys; most abundant south of latitude 29°, following the coast with wide thickets and ascending the rivers for many miles; on Cape Sable and the shores of Bay Biscayne sometimes growing at a little distance from the coast on ground not submerged by the tide, and here attaining its largest size, with tall straight trunks and few aerial roots; on Bermuda, the Bahamas, the Antilles, the west coast of Mexico, lower California, the Galapagos Islands, and from Central America along the northeast coast of South America to the limits of the tropics.
XLVII. COMBRETACEÆ.
Trees or shrubs, with astringent juice, naked buds, and alternate or opposite simple entire coriaceous persistent leaves, without stipules. Flowers regular, perfect, or polygamous; calyx 5-lobed, the lobes valvate in the bud; petals 5, valvate in the bud, inserted at the base of the calyx, or 0; disk epigynous; stamens 5—10, inserted on the limb of the calyx; filaments slender, filiform, distinct, exserted; anthers introrse, 2-celled, the cells opening longitudinally; ovary 1-celled; style slender, subulate; stigma minute, terminal, entire; ovules usually 2, suspended from the apex of the cell, collateral, anatropous; raphe ventral; micropyle superior. Fruit drupaceous, often crowned with the accrescent calyx. Seed solitary; albumen 0; embryo straight, with convolute cotyledons; radicle minute, turned toward the hilum.