Climate controls the growth of plants most imperatively, and in the cultivation of his fruits, flowers, and culinary vegetables, it forms the first object of the gardener's inquiry. He must first know the climate in which any givnen plant is native; and secondly, the soil which it affects, before he can cultivate it successfully. How all-influential is climate appears from the fact, that different countries have often a totally different Flora on soils similar in constitution. Thus, as is observed by Decandolle and Sprengel, in The Philosophy of Plants, "there are a great many perfect plants which exclusively belong to the tropics, which never pass beyond them, and which are found equally in Asia and Africa, in America and the South Sea Islands, and even in New Holland. Although, as we have said, these are rather families, as Palmae Scitamineae, Museae, Sapin-deae, and Anoneae; or genera, as Epi-dendrum, Santalum, Olax, Cymbidium, and so forth; yet there are particular species, which grow in all parts of the world only between the tropics, as for instance, Heliotropium Indicum, Age-ratum conyzoides, Pistiae stratiotes, Scoparia dulcis, Guilandina Bonduc, Sphenocleae zeylanica, Abrus precato-rius, Boerhavia mutabilis, and so forth.

But most commonly there are other species, which, under the same degree of latitude, supply in the new world the place of related species in the old. Dryas octopetala, indeed, grows equally upon the mountains of Canada, and in Europe; but Dryas tenella of Pursh, which is very like the former, grows only in Greenland and Labrador. Instead of the Platanus Orientalis, there grows in North America the Platanus Occidentalis; instead of Pinus Cembra, in Europe and Asia, there grows in North America Pinus Strobus; instead of Prunus Laurocerasus,in Asia Minor, there grows under the same latitude in North America the Prunus Caroliniana. There are many exceptions to this rule, however, depending on circumstances that have been already noticed. In the first place, countries are wont to share their Floras with neighbouring regions, especially islands lying under the same latitude, as the Azores possess the Floras of Europe and of Northern Africa, rather than those of America, because they are scarcely ten degrees of longitude from the coast of Portugal. Sicily, and, still more, Malta, possesses a Flora made up of those of the South of Europe and the North of Africa. The Aleutian Islands share their Flora with the north-west coast of America, and the north-east of Asia. But the most distant countries, lying under the same latitude, may have the same or a similar vegetation, while countries or islands which lie between them, have not the least share in this particular Flora. The island of St. Helena, which is scarcely eighteen degrees of longitude from the west of Africa, and which lies a little further south than Congo, has yet no plants, which are found in those last-named regions. (Roxburgh's List of Plants seen in the Island of St. Helena, appended to Beatson's Island of St. Helena.) Japan has a great many plants common to Southern Europe, which, however, are not found in those regions of Asia that lie under the same latitude.

We must further remark, that the eastern countries of the old world, and the eastern shores of America, as far as the Alleghany Mountains, have a much lower temperature than the western regions; and that it is always colder in Siberia and the north-east of Asia, than under the same latitude in Europe; and, that even Petersburgh is colder than Upsal, and Upsal than Christiania; although they all three lie in the sixtieth degree of north latitude. In North America the difference is still greater, and there are commonly fifteen degrees of Fahrenheit's thermometer between the temperature of the east and west coast. It hence happens that many plants which in Norway grow under the polar circle, scarcely reach the sixtieth degree, on the limits between Asia and Europe. To this class belong the Silver Fir, Mountain Ash, Trembling Poplar, Black Alder, and Juniper. Even in the temperate zone, the vegetation of many trees ceases sooner in the east than in the west. In Lithuania and Prussia, under the fifty-third degree, neither vines nor peaches nor apricots thrive: at least their fruit does not ripen, as also happens in the middle of England. The most remarkable example of this great difference of temperature is furnished by the Mespi-lus Japonica, which grows at Nanga "Sacki, and Jeddo, under the thirty-third and thirty-sixth degrees of north latitude; and which also grows in the open air in England, under the fifty-second degree of north latitude, when it is planted against a wall. - Botanical Register, Vol. V.

The same degree of latitude in the southern and northern hemisphere, are connected with very different temperatures, and produce a completely different vegetation. This, however, must be understood rather of the temperate and frigid zones, than of the tropical climates, which, as we have already noticed, are pretty much the same over the whole earth. But the summer is shorter in the southern hemisphere, because the motion of the earth in her perigee is more rapid. The summer is there also colder, because the greater quantity of ice over the vast extent of sea requires more heat for dissolving it than can be obtained; as also because the sunbeams are not reflected in such quantity from the clear surface of the sea water, as to afford the proper degree of heat. It thence happens that in the southern hemisphere the Flora of the pole extends nearer the equator, than in the northern. Under the 53d and 54th degrees of latitude, we meet with plants which correspond with the Arctic Flora. In Magellan's Land, and in Terra del Fuego, Betula antarctica corresponds with Betula nana in Lapland; Empctrum rubrum with Empe-trum nigrum - Arnica oporina with Arnica montana - Geum Magellanica with Geum rivale in England - Saxifraga Magellanica with Saxifraga rivularis in Finmark. Instead of Andromeda tetra-gona and hypnoides of Lapland, Terra del Fuego produces Andromeda myrsi-nites; in place of Arbutus alpina and Uva ursi of the Arctic polar circle, Terra del Fuego produces Arbutus mu-cronata, microphylla, and pumila.

Aria antarctica reminds us of the Holcus alpina of Wahlenburgh; and Pinguicula antaretica recalls to our recollection Pinguicula alpina. We must recollect, however, that in South America the great mountain chains of the Andes stretch from the tropical regions, almost without interruption, to the Straits of Magellan (from the 52d to the 53d degree of S. lat.), and that, on this account, tropical forms are seen in that frigid southern zone, because the tract of mountains everywhere determines tation. It is hence that the straits of .Magellan are prolific of Coronariae, Onagrae, Dorsteniae, and Heliotropiae, which in other parts of the world grow only within the tropics, or in their neighbourhood. In general the vegetation of the southern hemisphere is very different from that of the northern; and there is a certain correspondence between the Floras of Southern Africa, America, and New Holland. Most of the trees are woody with stiff leaves, blossoms sometimes magnificent, but fruit of little flavour. In Southern Africa, as well as in New Hollaud, it is the form of the Proteae which prevails, as if appropriated to these regions.

Instead of the South American Erica;, we find the Epacridae of New Holland; Lobeliae, Diosmae, and a great number of rare forms of compound blossoms and of umbellatae, are common to all these southern regions".

Now, the reason for these differences is, that the countries thus contrasted differ in climate - that is, they differ in the intensity and duration of light and heat they enjoy - they differ in the contrast of their day and night temperatures - they differ in the relative length of the day and night - they differ in the length of their summer and winter, or, which is synonymous, in the relative length of their periods of vegetable activity and rest - they differ also in the amount of rain which fills, not only annually, but at particular seasons - they differ in having much atmospheric moisture deposited in the form of rain or dew, or snow, at different periods of vegetable activity or rest. Now, whatever these differences are, whatever the peculiarities of a climate are from which a plant comes, the gardener cannot cultivate it successfully unless he secures to that plant those climatal differences and peculiarities.