They contain stunted timber trees, palms, mangroves and other tropical and sub-tropical plants and have an almost impenetrable undergrowth.
The coastlands of Natal and Portuguese East Africa, the vegetation is abundant, and mangroves, palms, baobab and bombax trees flourish.
The west coast throughout its whole length is covered to a depth of some miles with mangrove swamps, with only a few isolated stretches of sandy beach, the dim foliage of the mangroves and the hideous mud flats presenting a depressing spectacle.
From the sea the only indication of a river mouth is a break in the dark green mangroves which here universally fringe the coast.
Studer (Crustacea of the Gazelle, 1882) records Balanus amphitrite (Darwin?) from roots and stems of mangroves in the Congo, where, he says, " it follows the mangroves as far as their vegetation extends along the stream, to six sea-miles from the mouth."