Nuevo Leon lies partly upon the great Mexican plateau and partly upon its eastern slopes, the Sierra Madre Oriental crossing the state N.W.
Less is definitely known of the elevated regions of Chiapas, on the border of Guatemala, which are separated from the great Mexican Plateau by the low Isthmus of Tehuantepec (718 ft.
Crossing the highest part of the Mexican Plateau is a broken series of ranges, which form the water-parting between its northern and southern slopes.
The most common plants of the Mexican plateau are the agaves, yuccas and cacti, each of which is represented by a number of species.
About one thousand species have been described, a very large percentage of which are to be found on the Mexican plateau.