The family of the ferns is spread over the whole earth, but chiefly abounds in the vicinity of the tropics. Most of these plants love the shady and damp ground of the primitive forest, others attach themselves with their roots to rocks or trees. In the equatorial regions several of their species attain arboreal dimensions, with stems from twelve to thirty feet high and extensive crowns of large fronds, imitating the stately tufts of palms. But they do not possess the noble elegance of these kings of the vegetable world; and their stems, of a sombre brown colour, are rather an image of decrepid old age than of the youthful vigour which we admire in the growth of the palms. They do not seem to love the highest temperature of the equator, but rather the milder climate of the mountainous regions near the tropics. Here they frequently stand singly in the thicket, particularly where a waterfall impregnates the air with moisture, or on the borders of sources and ponds. No parasites settle upon them, no bird constructs its nest among their fronds, no quadruped burrows in the mouldy ground where they take root, even the ants disdain to build on their sapless stems, and thus they make the impression of friendless aliens in a convivial group. [Illustration: ARECA PALM.] [Illustration: THE BANANA AND THE PLANTAIN.] CHAPTER XIV. THE CHIEF ESCULENT PLANTS OF THE TORRID ZONE. Rice--Various Aspect of the Rice-fields at different Seasons--The Rice-Bird--Maize--First imported from America by Columbus--Its enormous Productiveness--Its wide zone of Cultivation--Millet, Dhourra--The Bread-Fruit Tree--The Bananas--Their ancient Cultivation--Avaca or Manilla Hemp--Humboldt’s Remarks on the Banana--The Traveller’s Tree of Madagascar--The Cassava Root-- Tapioca--Yams--Batatas--Arrowroot--Taro--Tropical Fruit Trees-- The Chirimoya--The Litchi--The Mangosteen--The Mango. Of all the cereals there is none that affords food to so vast a multitude as the rice-plant (_Oryza sativa_), on whose grains from time immemorial the countless millions of south-eastern Asia chiefly subsist. From its primitive seat, on the Ganges or the Sikiang, its cultivation has gradually spread not only over the whole tropical zone, but even far beyond its bounds, as it thrives both in the swamps of South Carolina and in the rich alluvial plains of the Danube and the Po. Along the low river banks, in the delta-lands which the rains of the tropics annually change into a boundless lake, or where, by artificial embankments, the waters of the mountain streams have been collected into tanks for irrigation, the rice-plant attains its utmost luxuriance of growth, and but rarely deceives the hopes of the husbandmen.