It is under the burning rays of a tropical sun that vegetation displays its most majestic forms. In the cold north the bark of trees is covered with lichens and mosses, whilst between the tropics the Cymbidium and fragrant Vanilla enliven the trunks of the Anacardias, and of the gigantic fig trees. The fresh verdure of the Pothos leaves, and of the Dracontias, contrasts with the many-coloured flowers of the Orchideæ. Climbing Bauhinias, Passifloras, and yellow flowering Banisterias, twine round the trunks of the forest trees. Delicate blossoms spring from the roots of the Theobroma, and from the thick and rough bark of the Crescentias and the Gustavia.[35] In the midst of this profusion of flowers and fruits, and in the luxuriant intertwinings of the climbing plants, the naturalist often finds it difficult to discover to which stem the different leaves and flowers really belong. A single tree adorned with Paullinias, Bignonias, and Dendrobium, forms a group of plants which, if disentangled and separated from each other, would cover a considerable space of ground. In the tropics vegetation is generally of a fresher verdure, more luxuriant and succulent, and adorned with larger and more shining leaves than in our northern climates. The “social” plants, which often impart so uniform and monotonous a character to European countries, are almost entirely absent in the Equatorial regions. Trees almost as lofty as our oaks are adorned with flowers as large and as beautiful as our lilies. On the shady banks of the Rio Magdalena in South America, there grows a climbing Aristolochia bearing flowers four feet in circumference, which the Indian boys draw over their heads in sport, and wear as hats or helmets.[36] In the islands of the Indian Archipelago the flower of the Rafflesia is nearly three feet in diameter, and weighs above fourteen pounds. The great elevation attained in several tropical countries not only by single mountains but even by extensive districts, enables the inhabitants of the torrid zone--surrounded by palms, bananas, and the other beautiful forms proper to those latitudes--to behold also those vegetable forms which, demanding a cooler temperature, would seem to belong to other zones. Elevation above the level of the sea gives this cooler temperature even in the hottest parts of the earth; and Cypresses, Pines, Oaks, Berberries and Alders, (nearly allied to our own) cover the mountainous districts and elevated plains of Southern Mexico and the chain of the Andes at the Equator. Thus it is given to man in those regions to behold without quitting his native land all the forms of vegetation dispersed over the globe, and all the shining worlds which stud the heavenly vault from pole to pole.[37]