It is beneath the glowing rays of a tropical sun, that the noblest forms of vegetation are developed. In the cold North the bark of trees is covered only with dry lichens and mosses, while beneath the tropics the Cymbidium and the fragrant Vanilla adorn the trunks of the Anacardias and the gigantic Fig-tree. The fresh green of the Pothos leaves and of the Dracontias contrast with the many coloured blossoms of the Orchideæ; climbing Bauhinias, Passion-flowers and golden flowered Banisterias encircle every tree of the forest. Delicate blossoms unfold themselves from the roots of the _Theobroma_, and from the thick and rough bark of the _Crescentia_ and _Gustavia_[105]. Amid this luxuriant abundance of flowers and foliage, amid this exuberance and tangled web of creeping plants, it is often difficult for the naturalist to recognise the stems to which the various leaves and blossoms belong. A single tree, adorned with Paullinias, Bignonias, and Dendrobias, forms a group of plants, which, separated from each other, would cover a considerable space of ground. In the tropics, plants are more succulent, of a fresher green, and have larger and more glossy leaves, than in the northern regions. Social plants, which give such a character of uniformity to European vegetation, are almost wholly absent in the equatorial zone. Trees, almost twice as high as our oaks, there bloom with flowers as large and splendid as our lilies. On the shady banks of the Magdalena River, in South America, grows a climbing _Aristolochia_, whose blossoms, measuring four feet in circumference, the Indian children sportively draw on their heads as caps[106]. In the South Indian Archipelago, the flower of the Rafflesia is nearly three feet in diameter, and weighs above fourteen pounds. The extraordinary height to which not only individual mountains but even whole districts rise in tropical regions, and the consequent cold of such elevations, affords the inhabitant of the tropics a singular spectacle. For besides his own palms and bananas, he is surrounded by those vegetable forms which would seem to belong solely to northern latitudes. Cypresses, pines, and oaks, barberry shrubs and alders (nearly allied to our own species) cover the mountain plains of Southern Mexico and the chain of the Andes at the equator. Thus nature has permitted the native of the torrid zone to behold all the vegetable forms of the earth without quitting his own clime, even as are revealed to him the luminous worlds which spangle the firmament from pole to pole[107].