AGRICULTURE--DRY AND RAINY SEASONS.--IRRIGATION--YIELD OF CORN LANDS.--COLONIAL RESTRICTIONS.--COLONIAL DEPENDENCE--BAD INTERCOMMUNICATION--ARRIEROS.--CORN LANDS--DIFFERENT KINDS OF CORN IN MEXICO--MODE OF CULTIVATION--PRODUCTION--VARIOUS USES OF CORN.--BANANA--MAINOC--RICE.--THE OLIVE--VINE--CHILE PEPPER--TOMATO--FRIJOL--MAGUEY.--MAGUEY ESTATES.--MAKING PULQUE.--ALOES--CACTI. Sun, seasons, temperature, soils and moisture are the chief elements of agricultural success or failure, according as they are beneficially harmonized or unfortunately disunited. In our geological and geographical descriptions we have already indicated the rapid changes of temperature in Mexico experienced by rising gradually from the sea shore to the summit of the table land, and passing through the _tierras calientes_, _templadas_ and _frias_. This is the origin of the variety of Mexican productions and the reason why the pine and the palm are encountered upon the same parallel of latitude; but the _fertility_ of Mexico is very much governed by the moisture with which it is annually favored, and for which it is obliged to rely chiefly on the clouds. The Mexicans are not accustomed to separate the year as we do into the four seasons of spring, summer, autumn and winter, for the variation of temperature scarcely authorizes such marked distinctions of climate; yet they divide the twelve months into two grand divisions of _El Estio_--or the dry season, and _La Estacion de las aguas_, or the rainy season. The latter commences about May and lasts usually four months, whilst the dry season comprises the remainder of the year. The curving shores of Mexico along the gulf and interior highlands gather and hem in an immense body of vapor, which is carried on by the trade winds and condensed against the cold and lofty inland mountain peaks which rise above the limit of perpetual congealation. This occurs during the dry season whilst the sun is at the south. But when the power of that luminary increases as it advances northward, and until it has long turned back again on its southern course, these vapors are dissolved by the hot intertropical air and descend, almost daily, in fertilizing showers. The [Illustration: GROUP OF PLANTS.]