Page:The Botany of the Antarctic Voyage.djvu/96

74 Pole than these are to the opposite one. Iceland for instance, in lat. 62&deg; N., proverbially barren as it is, and upon which no tree, but a few stunted birches, is to be found, contains certainly five times as many flowering plants as Lord Auckland's group and Campbell's Island together, whose rich vegetation is evident on their being first approached from sea; and yet the numerical proportion which the two great groups of flowering plants bear to one another in each country is almost identical. Kerguelen's Land is on the southern limit of vegetation in its own longitude, as we may presume from its containing only eighteen species of flowering plants; but these cover as much of the surface of the island as the plants of Spitzbergen do, and yet the latter country contains forty-five species, though on the verge of Arctic vegetation and infinitely nearer the Pole. Lastly, on Walden Island (lat. 80&frac12;&deg; N.) we have the last traces of ph&aelig;nogamic plants in the northern hemisphere, and in the opposite one beyond the South Shetlands (63&deg; S.) no flowering plants exist; but whilst the former islet boasts of ten species of flowering plants, the latter contains but a solitary grass.

The uniformity of the Flora at the different levels in any given island of the South is to be expected from the paucity of species, and we further find that these are spread over vast extents of country. This is remarkably the case with the southern American Flora, where the northern limit at which the antarctic Beech grows near the sea is 45&deg;, from which latitude as far as 56&deg; S. the level of the ocean seems to be its natural habitat: again, the plants which form the bogs of the Chonos Archipelago in lat. 45&deg; S. are the same as those of Cape Horn, and the general features of the vegetation of the two localities are the same. In the northern temperate regions a very different state of things will be found to prevail: compare the Flora of the south of France, in the latitude of the Chonos Archipelago, with that of Argyleshire in the parallel of Cape Horn, and how little similarity exists; and this not only because the plants of France cannot bear the climate of Scotland, but because new forms are developed in the latter country, equally unsuited to the south of France. Many parallel cases to this might be adduced, all tending to prove that there are conditions in the physical geography of the southern islands which render them unfavourable to the production of species, but which are accompanied with a luxuriant development of such as do exist: and further, that species which form the mass of the vegetation under these conditions are such as continue to be typical of the Flora through many degrees of latitude whose mean temperature is considerably different.

The equable climate which these countries now under consideration enjoy, is doubtless mainly attributable to the vast body of ocean surrounding them; and though the want of new species must in a measure depend on the limited extent of surface for their development, it is not altogether from the want of space that the paucity of new forms in proceeding to the South is to be accounted for, since in no other part of the globe can sixteen degrees of so luxuriant a Flora composed of so few species be traversed.

All parts of antarctic America as it is called, a name its ungenial climate alone, and not its geographical position, warrants, are wet, foggy and cold; snow-storms and gales of wind prevail throughout the year; and not only on the hills, for the atmosphere seems so loaded with moisture, that a precipitation on the upper regions is generally followed at once by rain or snow on the lower grounds. In the summer the sun scarcely exerts any power without raising mists which intercept its rays. The difference between the summer and winter temperature is small, and the diurnal changes trifling. The perennial hurricanes which sweep the exposed surfaces of the hills seem alone materially to check the vegetation, for even on the mountains the plants of the plains reappear wherever a shelter is afforded. In no part of Scotland does 1700 feet of elevation exist without showing a material change in the vegetable kingdom, such a height producing many subalpine and even alpine plants not met with at the level of the ocean; but though in Hermite Island the mountains attain that height, there is scarcely a plant growing upon them which does not equally exist in the open grounds near the sea. Nor is there probably any country where the prevailing species, forming the mass of the Flora, have such wide ranges as in Antarctic America.

From this we may presume, that plants will pass through many degrees of latitude, and consequently from