MANGROVE. The remarkable "mangrove forests" which fringe tidal estuaries, overrun salt marshes, and line muddy coasts in the tropics of both Old and New Worlds, are composed of trees and shrubs belonging mainly to the family Rhizo phoraceae, but including, especially in the eastern mangrove for mations of Further India and the Malay Archipelago, members of other families, such as Lythraceae (Sonneratia), Verbenaceae (Avicennia), and the acaulescent Nipa-palm. Their trunks and branches constantly produce adventitious roots, which, descending in arched fashion, strike at some distance from the parent stem, and send up new trunks, the forest thus spreading like a banyan grove. An advantage in dispersal, very characteristic of the order, is afforded by the seeds, which have a striking peculiarity of germination. While the fruit is still attached to the parent branch the long radicle emerges from the seed and grows rapidly down wards. When the seed falls the young root is in the right position
to be driven into the mud ; the plant being thus rooted the plumule makes its appearance. The young root may grow to such a length that it becomes fixed in the mud before the fruit separates from the parent tree. An interesting feature of the mangrove is the air-roots, erect or kneed branches of the roots, which project above the mud, and are provided with minute openings (lenticels), into which the air diffuses and then passes by means of passages in the soft spongy tissue to the roots which spread beneath the mud. The wood of some species is hard and durable, and the astringent bark is used in tanning, yielding catch. The fruit of the common mangrove, Rhizophora Mangle, is sweet and whole some.