In The Third Zone (Beginning At Nine Hundred Toises Of Absolute Height), The Last Groups Of Arbutus, Of Myrica Faya,

And of that beautiful heath known to the natives by the name of Texo, appear. This zone, four hundred toises

In breadth, is entirely filled by a vast forest of pines, among which mingles the Juniperus cedro of Broussonnet. The leaves of these pines are very long and stiff, and they sprout sometimes by pairs, but oftener by threes in one sheath. Having had no opportunity of examining the fructification, we cannot say whether this species, which has the appearance of the Scotch fir, is really different from the eighteen species of pines with which we are already acquainted in Europe. M. Decandolle is of opinion that the pine of Teneriffe is equally distinct from the Pinus atlantica of the neighbouring mountains of Mogador, and from the pine of Aleppo,* (* Pinus halepensis. M. Decandolle observes, that this species, which is not found in Portugal, but grows on the Mediterranean shores of France, Spain, and Italy, in Asia Minor, and in Barbary, would be better named Pinus mediterranea. It composes the principal part of the pine-forests of the south-east of France, where Gouan and Gerard have confounded it with the Pinus sylvestris. It comprehends the Pinus halepensis, Mill., Lamb., and Desfont., and the Pinus maritima, Lamb.) which belongs to the basin of the Mediterranean, and does not appear to have passed the Pillars of Hercules. We met with these last pines on the slope of the Peak, near twelve hundred toises above the level of the sea. In the Cordilleras of New Spain, under the torrid zone, the Mexican pines extend to the height of two thousand toises. Notwithstanding the similarity of structure existing between the different species of the same genus of plants, each of them requires a certain degree of temperature and rarity in the ambient air to attain its due growth. If in temperate climates, and wherever snow falls, the uniform heat of the soil be somewhat above the mean heat of the atmosphere, it is probable that at the height of Portillo the roots of the pines draw their nourishment from a soil, in which, at a certain depth, the thermometer rises at most to nine or ten degrees.

The fourth and fifth zones, the regions of the retama and the gramina, occupy heights equal to the most inaccessible summits of the Pyrenees. It is the sterile part of the island where heaps of pumice-stone, obsidian, and broken lava, form impediments to vegetation. We have already spoken of those flowery tufts of alpine broom (Spartium nubigenum), which form oases amidst a vast desert of ashes. Two herbaceous plants, the Scrophularia glabrata and the Viola cheiranthifolia, advance even to the Malpays. Above a turf scorched by the heat of an African sun, an arid soil is overspread by the Cladonia paschalis. Towards the summit of the Peak the Urceolarea and other plants of the family of the lichens, help to work the decomposition of the scorified matter.

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