As the banana form shows the greatest expansion, so the greatest contraction of foliage is shown in Casuarinas, and in the form of needle-trees (Coniferæ). Pines, thuias, and cypresses belong to this form, which prevails in northern regions, and is comparatively rare within the tropics: in Dammara and Salisburia the leaves, though they may still be termed needle-shaped, are broader. In the colder latitudes, the never-failing verdure of this form of trees cheers the desolate winter landscape, and tells to the inhabitants of those regions that when snow and ice cover the ground the inward life of plants, like the Promethean fire, is never extinct upon our planet. Like mosses and lichens in our latitudes, and like Orchideæ in the tropical zone, plants of the Pothos form clothe parasitically the trunks of aged and decaying forest trees: succulent herbaceous stalks support large leaves, sometimes sagittate, sometimes either digitate or elongate, but always with thick veins. The flowers of the Aroideæ are cased in hooded spathes or sheaths, and in some of them when they expand a sensible increase of vital heat is perceived. Stemless, they put forth aerial roots. Pothos, Dracontium, Caladium, and Arum all belong to this form, which prevails chiefly in the tropical world. On the Spanish and Italian shores of the Mediterranean, Arums combine with the succulent Tussilago, the acanthus, and thistles, which are almost arborescent, to indicate the increasing luxuriance of southern vegetation. Next to the last-mentioned form, of which the Pothos and Arum are representatives, I place a form with which, in the hottest parts of South America, it is frequently associated--that of the tropical twining rope-plants, or Lianes, which display in those regions, in Paullinias, Banisterias, Bignonias, and Passifloras, the utmost vigor of vegetation. It is represented to us in the temperate latitudes by our twining hops and by our grapevines. On the banks of the Orinoco the leafless branches of the Bauhinias are often between 40 and 50 feet long; sometimes they hang down perpendicularly from the high top of the Swietenia, and sometimes they are stretched obliquely like the cordage of a ship; the tiger-cats climb up and descend by them with wonderful agility.