1093. Hence it is that plants of high latitudes live on the mountains of such as are much lower, and thus the plants of Greenland and Lapland are found on the Alps and Pyrenees. At the foot of Mount Ararat, Tournefort met with plants peculiar to Armenia ; above these he met with plants which are found also in France; at a still greater height he found himself surrounded with such as grow in Sweden ; and at the summit, with such as vegetate in the polar regions. This accounts for the great variety of plants which are often found in a Flora of no great extent; and it may be laid down as a botanical axiom, that the more diversified the surface of the country, the richer will its flora be, at least in the same latitudes. It accounts also, in some cases, for the want of correspondence between plants of different countries, though placed in the same latitudes; because the mountains, or ridges of mountains, which may be found in the one and not in the other, will produce the greatest possible difference in the character of their Floras. And to this cause may generally be ascribed the diversity that often actually exists between plants growing in the same latitudes, as between those of the north-west and north-east coasts of North America; as also of the south-west and south-east coasts; the former being more mountainous, the latter more flat. Sometimes the same sort of difference takes place between the plants of an island and those of the neighbouring continent; that is, if the one is mountainous and the other flat; but if they are alike in their geographical delineation, then they are generally alike in their vegetable productions.
