The Rhododendron Of Switzerland, In Those Places Where It Grows, At The Elevation Of Between Eight Hundred And A Thousand Toises, Belongs To A Climate, The Mean Temperature Of Which Is +2 And-1 Degrees, Like That Of The Plains Of Lapland.

In this zone the coldest months are-4, and-10 degrees:

The hottest, 12 and 7 degrees. Thermometrical observations, made at the same heights and in the same latitudes, render it probable that, at the Pejual of the Silla, one thousand toises above the Caribbean Sea, the mean temperature of the air is still 17 or 18 degrees; and that the thermometer keeps, in the coolest season, between 15 and 20 degrees in the day, and in the night between 10 and 12 degrees. At the hospital of St. Gothard, situated nearly on the highest limit of the rhododendron of the Alps, the maximum of heat, in the month of August at noon, in the shade, is usually 12 or 13 degrees; in the night, at the same season, the air is cooled by the radiation of the soil down to +1 or-1.5 degrees. Under the same barometric pressure, consequently at the same height, but thirty degrees of latitude nearer the equator, the befaria of the Silla is often, at noon, in the sun, exposed to a heat of 23 or 24 degrees. The greatest nocturnal refrigeration probably never exceeds 7 degrees. We have carefully compared the climate, under the influence of which, at different latitudes, two groups of plants of the same family vegetate at equal heights above the level of the sea. The results would have been far different, had we compared zones equally distant, either from the perpetual snow, or from the isothermal line of 0 degrees.* (* The stratum of air, the mean temperature of which is 0 degrees, and which scarcely coincides with the superior limit of perpetual snow, is found in the parallel of the rhododendrons of Switzerland at nine hundred toises; in the parallel of the befarias of Caracas, at two thousand seven hundred toises of elevation.)

In the little thicket of the Pejual, near the purple-flowered befaria, grows a heath-leaved hedyotis, eight feet high; the caparosa,* which is a large arborescent hypericum (* Vismia caparosa (a loranthus clings to this plant, and appropriates to itself the yellow juice of the vismia); Davallia meifolia, Heracium avilae, Aralia arborea, Jacq., and Lepidium virginicum. Two new species of lycopodium, the thyoides, and the aristatum, are seen lower down, near the Puerto de la Silla.); a lepidium, which appears identical with that of Virginia; and lastly, lycopodiaceous plants and mosses, which cover the rocks and roots of the trees. That which gives most celebrity in the country to the little thicket, is a shrub ten or fifteen feet high, of the corymbiferous family. The Creoles call it incense (incienso).* (* Trixis nereifolia of M. Bonpland.) Its tough and crenate leaves, as well as the extremities of the branches, are covered with a white wool. It is a new species of Trixis, extremely resinous, the flowers of which have the agreeable odour of storax.

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