In the Southern region the vegetation somewhat resembles that of the tropics, being a transition between that of the temperate and torrid zones. Walnuts, elms, chestnuts, and oaks are found there, and with them three species of palms, one of which is _Chamærops Palmetto_; species of _Yucca_; of _Zamia_, among the _Cycadaceæ_; _Passiflora_; of woody twining plants, such as _Bignonia sapindus_; cacti, and laurels. Lastly, by the side of tulip-trees, _Pavia_, and _Robinia_, grow magnificent species of _Magnolia_, of which this is the true domain. The vegetation of this region is thus remarkable in its variety. The sugar-cane, indigo, cotton, and tobacco cover the cultivated plains. In Missouri, Texas, Arkansas, and Mexico, the great colony of the cacti raise their lofty stems. In this region _Cactus_, _Opuntia_, _Cereus_, _Echinocactus_, and _Melocactus_, raise their oddly branching stems and clustering flowers, the most remarkable of all doubtless being _Cereus giganteus_. It inhabits the wildest and most inaccessible regions, requiring little or no soil to attain a prodigious development. It has at first the appearance of an enormous tomahawk. Thence rises a column, three yards high, which branches off and assumes the shape of an immense candelabrum, the height of which may be twelve or thirteen yards. Mexico, according to the reports of botanists, may be divided into three regions of altitude. The first extends from the valleys as far as the oak forests--this is the region of palms, cotton, indigo, sugar-cane, coffee, and tropical fruits. The second, situated at an elevation of from 3,500 to 9,000 feet above the sea, is the temperate region. It stretches from the oak forests to the forests of _Coniferæ_. At this height the temperature is still sufficient to ripen some tropical fruits. The third, or cold region, occupies a space comprehended between the Conifers and perpetual snow. In many places it possesses a climate under which pear, apple, and cherry trees, and the potato, can still grow. In ascending from the foot of Orizaba, one sees successively appear and disappear _Mimosa_, _Acacia_, cotton, _Convolvulus_, _Bignonia_, oaks, palms, bananas, myrtles, laurels, _Terebinthaceæ_, tree-ferns, _Magnolia_, arborescent composites, plane, _Storax_, apples, pears, cherries, apricots, pomegranates, lemon and orange trees, orchids, _Fuchsia_, and _Cactus_.