Mangrove (Rhizophora), a genus of calycifloral dicotyledons, including about fifty species, of which the indistinct affinities have constituted a separate order (Rhizophoraceæ). They are trees and shrubs, all tropical (especially South American), and natives of coasts, particularly about the mouths of rivers, where they grow in the mud, and form a close thicket down to and within the margin of the sea, even to low-water mark, forming the characteristic mangrove-swamps so often described by travellers and naturalists. Most species send down roots from their branches, and thus rapidly extend over large spaces, forming secure retreats for multitudes of aquatic birds, whilst crabs and shell-fish are also to be found in them in vast numbers. Their interlacing roots retain mud, seaweed, &c., and thus rapidly form soil and encroach upon the shallow sea; on the north coast of Java and elsewhere their geological importance is specially marked. The seeds have the peculiarity of germinating before the fruit has fallen, a long thick radicle proceeding from the seed, piercing its covering, and extending rapidly downwards. When the fruit drops, the stout heavy radicle pierces the mud, and the young tree is thus planted in the proper position forthwith. The fruit of the common mangrove (R. Mangle) is sweet, eatable; and its juice, when fermented, yields a light wine. The bark is sometimes imported for the sake of its tannin, in which all the species are rich. Mangrove wood is also imported from the West Indies. The Chinese and East Indian species (R. gymnorhiza, &c.) are of similar habit and properties; some of the latter are separated as a distinct genus, Bruguiera.—The so-called White Mangrove is Avicennia (q.v.).