Six zones of vegetation have we thus passed through, in which the continually increasing temperature of the climate called forth ever a different, ever a more luxuriant vegetation, and we conclude our wanderings, after a short rest under the five-thousand-yeared Dracænas, by climbing the Pic of Teyde. Man has taken possession of the soil of the plain at its foot and dislodged the original vegetation. Through vineyards and maize-fields we ascend, till the shades of the evergreen bay-laurel surround us. Trees of the lace-bark tribe and similar plants succeed; we wander for a time through a _zone of evergreen forest trees_. At a height of 4,000 feet we lose the plants which had so far accompanied us. A very small number of peculiar plants mark a quickly traversed _zone of deciduous trees_, and we come among the resinous trunks of the Canary pine. A _zone of conifers_ shield us from the sun’s rays up to a height of 6,000 feet, then the vegetation suddenly becomes low--from humble bushes it passes into a flora which bears all the characters of the Alpine plants, till finally the naked rock sets a limit to all organic life, and no snow and ice bedeck the summit of the mountain, only because its height of 12,236 feet does not, in a position so near the tropics, extend up to the region of eternal snow. Counting by the limits of vegetation, we have resurveyed in a few hours’ climb the wide way from Spitzbergen to the Canaries, an extent of more than fifty degrees of latitude. The plant is dependent on the condition of the soil, in the widest sense of the word, on the store of nutriment it contains, and on all that influences the chemical process of formation, consequently, above all, upon a determinate temperature. The universal, indispensable nutrient substance of plants, and, at the same time, the matter by means of which all the rest are conveyed into it, is water. Without water there is no vegetation. The orchidaceous plants of the tropical forest let their peculiarly constructed roots hang down from the branch to which they cling in the warm, moist atmosphere, and absorb water in the form of vapor. Our water-lilies and the proper bog-plants will only flourish when surrounded by liquid water, or, at least, with their roots dipping in it. The case is quite different with the great majority of plants; they have to extract their nutriment from the earth, which contains the moisture to be absorbed into them in a peculiar condition. If to these three classes of air, water, and earth-plants we add one more, namely, the true parasites, which, like our dodder, draw their organized nutriment from other plants, we have obtained the principal divisions of stations.