If the geology and topography of Mexico are marked and peculiar, the organic world also presents its own remarkable conditions; for, as to its _flora_ and _fauna_, Mexico is a land of transition, between North America on the one hand and Central and South America on the other, and contains the species of both regions, in the animal and vegetable kingdoms. As may well be imagined from such peculiar conditions, Mexico is a country whose _flora_ and _fauna_ are diverse and extensive. Indeed, as regards the former, every vegetable product found from the Equator to the Polar Circle exist in the country. The soil, in the tropical regions, as a result of high temperature and excessive moisture, is deep and fertile, both from the rock-decay consequent upon such conditions, and the deposit of organic matter from the profuse vegetation. In the region of the high plateau the product of rock-disintegration added to that caused by volcanic matter, and the sediment of dried-up lagoons of very recent time, have produced a great depth of soil in places, as before described, covering vast expanses, and this soil is found to be of exceeding fertility under irrigation. The conditions regarding irrigation are very marked in the region of the Nazas. On the one hand we encounter dry, bare, and uncultivated wastes; on the other verdant fields of cotton. Why is this? Both the lands are of a similar character of soil, but one is above the line of the irrigation canal, and the other below. No description of Mexico can be complete which does not sound the praises of her varied _flora_. The most striking characteristic of the flowers of this land, as has often been remarked, is the richness and brilliance of their colour. The floating gardens, and the canoe-loads of flowers and altar adornments of such which the Aztecs used and trafficked in, bore witness to aboriginal appreciation of these. To-day the flower-market of the capital is one of its attractions, whilst in the valley of Mexico not a day in the year lacks roses, lilies, camellias, strawberries, _et hoc genus omne_.