Such Are The General Phenomena Of The Distribution Of Plants.

It is now said that a mountain is high enough to enter into the limits of the rhododendrons and the befarias, as it has long been said that such a mountain reached the limit of perpetual snow.

In using this expression, it is tacitly admitted, that under the influence of certain temperatures, certain vegetable forms must necessarily be developed. Such a supposition, however, taken in all its generality, is not strictly accurate. The pines of Mexico are wanting on the Cordilleras of Peru. The Silla of Caracas is not covered with the oaks which flourish in New Grenada at the same height. Identity of forms indicates an analogy of climate; but in similar climates the species may be singularly diversified.

The charming rhododendron of the Andes (the befaria) was first described by M. Mutis, who observed it near Pamplona and Santa Fe de Bogota, in the fourth and seventh degree of north latitude. It was so little known before our expedition to the Silla, that it was scarcely to be found in any herbal in Europe. The learned editors of the Flora of Peru had even described it under another name, that of acunna. In the same manner as the rhododendrons of Lapland, Caucasus, and the Alps* (* Rhododendron lapponicum, R. caucasicum, R. ferrugineum, and R. hirsutum.) differ from each other, the two species of befaria we brought from the Silla* (* Befaria glauca, B. ledifolia.) are also specifically different from that of Santa Fe and Bogota.* (* Befaria aestuans, and B. resinosa.) Near the equator the rhododendrons of the Andes (Particularly B. aestuans of Mutis, and two new species of the southern hemisphere, which we have described under the name of B. coarctata, and B. grandiflora.) cover the mountains as far as the highest paramos, at sixteen and seventeen hundred toises of elevation. Advancing northward, on the Silla de Caracas, we find them much lower, a little below one thousand toises. The befaria recently discovered in Florida, in latitude 30 degrees, grows even on hills of small elevation. Thus in a space of six hundred leagues in latitude, these shrubs descend towards the plains in proportion as their distance from the equator augments. The rhododendron of Lapland grows also at eight or nine hundred toises lower than the rhododendron of the Alps and the Pyrenees. We were surprised at not meeting with any species of befaria in the mountains of Mexico, between the rhododendrons of Santa Fe and Caracas, and those of Florida.

In the small grove which crowns the Silla, the Befaria ledifolia is only three or four feet high. The trunk is divided from its root into a great many slender and even verticillate branches. The leaves are oval, lanceolate, glaucous on their inferior part, and curled at the edges. The whole plant is covered with long and viscous hairs, and emits a very agreeable resinous smell. The bees visit its fine purple flowers, which are very abundant, as in all the alpine plants, and, when in full blossom, they are often nearly an inch wide.

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