10. So far as concerns the flora of the country, four different types present themselves. The beach, the river-swamp, the forest, the grass-lands present their characteristic forms of plant-life. Five-sixths of the Republic are covered with the densest tropical forest; an enormous variety of gigantic trees grow closely crowded together and are bound by a tangle of vines and creeping plants into an almost impenetrable mass. Nowhere perhaps in the world is there a more typical tropical forest. The lower reaches of the rivers are bordered by a thicket of mangroves and pandanus, the former by its curious mode of growth--throwing downward from its branches almost vertical aerial roots which reach the water and strike down into the soft, oozy mud of the river-bottom--stretching far out from the banks themselves over the stream. Among the notable trees of Liberia are mahogany, ebony, and other valuable timber trees; camwood is abundant, and was formerly an object of important export for dyeing purposes; coffee grows wild and is of fine quality; there are various gum-producing trees, among them that which yields the gum arabic; the kola nut is common and has long been exported from the Grain Coast; there are various rubber-producing plants--the _funtumia_ and _landolphia_, the two most prized rubber-plants of Africa, occur abundantly--the former being a tree, the latter a vine; palms of many species occur; among them are the borassus or fan-palm, the calamus or climbing palm, the oil palm, a raphia, commonly known as the bamboo palm, which yields palm wine and the precious piassava fibre; notable is the great cotton-tree, which is considered sacred by the natives, no doubt on account of its strange appearance, due to enormous, thin, buttressing roots. There are flowers everywhere; water-lilies are common in the swamps, and lovely epiphytic orchids bloom upon the forest trees.