Note 157 — Chapter XXIII
Reading edition
M. de Candolle established 20 botanical regions, and Professor Schow the same number; but Professor Martius, of Munich, has divided the vegetation of the globe into 51 provinces, namely, 5 in Europe, 11 in Africa, 13 in Asia, 3 in New Holland, 4 in North and 8 in South America, besides Central America, the Antillas, the Antarctic Lands, New Zealand, Van Diemen’s Land, New Guinea, and Polynesia. To these, other divisions might be added, as the Galapagos, which is so strongly defined.
Baron Humboldt gives the following concise view of the distribution of plants, both as to height and latitude:—
The equatorial zone is the region of palms and bananas.
The tropical zone is the region of tree-ferns and figs.
The subtropical zone, that of myrtles and laurels.
The warm temperate zone, that of evergreen trees.
The cold temperate zone, that of European or deciduous trees.
The subarctic zone, that of pines.
The arctic zone, that of rhododendrons.
The polar zone, that of alpine plants.
Upper Limit of Trees on Mountains.—The upper limit of trees is distinguished by the Escalloniæ, on the Andes of Quito, at the height of 11,500 feet above the level of the sea.
In tropical Mexico, the upper limit of trees, at the height of 12,789 feet, is distinguished by the Pinus occidentalis.
In the temperate zone the limit of trees is marked by the Quercus Semicarpifolia, at 11,500 feet, on the south side of the Himalaya, and by the Betula Alba, on the north side, at the height of 14,000 feet: the same birch forms the limit on the Caucasus, at the elevation of 6394 feet. On the Pyrenees and Alps the limit is marked by the Coniferæ or pine tribe: on the Pyrenees by the Pinus uncinata, at the height of 10,870 feet; on the south side of the Alps by the larch, at the elevation of 6700 feet; and by the Pinus abies, at 5883 feet, on the north.
In Lapland, the Betula Alba forms the upper limit of trees, at the height of only 1918 feet.
The upper Limit of Shrubs.—In the Andes of Quito the Bejarias are the shrubs that attain the greatest height, and terminate at 13,420 feet above the sea-level.
The juniper, Salix, and Ribes, or currant tribe, form the upper limit of Shrubs on the south side of the Himalaya, at the height of 11,500 feet. The tama, or Genista versicolor, a species of broom, flourishes at the height of 17,000 feet on the north side, and vegetation is prolonged to nearly 18,000 feet.
The Rhododendron forms the upper limit of shrubs on the Caucasus, at 8825 feet; in the Pyrenees it grows to 8312 feet; in the Alps to 7480 feet; and in Lapland it forms the upper limit of shrubs at an elevation of 3000 above the Arctic Ocean.