an interesting statement respecting the plant vulgarly known by the name of the rose of Jericho, Anastatica Hierochuntina, growing in the arid wastes of Arabia and Palestine. By the time it dies, owing to the great drought, its tissue has become almost woody; its branches fold over each other till the whole mass assumes the form of a ball; its seedvessels have their valves tightly shut; and the plant remains adhering to the ground by a solitary branchless root. The wind, which always acts powerfully along the surface of a sandy plain, uproots this dry ball, and rolls it along. If it chance to meet with a splash of water during its constrained but necessary journey, it speedily imbibes the moisture, which causes the branches to unfold, and the pericarps to burst; and the seeds which could not have germinated if they had fallen on the dry ground, now sow themselves naturally in a moist soil, where they are able to grow, and where the young plant may support itself. The number of known species of plants on the surface of the earth, mentioned by botanists from the time of Theophrastus to the present day, is thus given, in a memoir on geographical botany by Mr. Hinds, who accompanied the late expedition of the Sulphur round the world, under the command of Sir Edward Belcher: Lindley, in 1835, gave the number at 86,000; but, according to Mr. Hinds, at the present time there are 89,000 species of plants described; and computing for countries scarcely examined, or as yet wholly unexplored, he supposes the total aggregate of species which vegetate on the earth to amount to about 133,000. This is an estimate which only goes a little beyond a similar calculation of De Candolle; and when we reflect that the interior of Africa, of Australia, and of the great islands of Oceanica, have not been visited by the geographer and the naturalist, the estimate will not be deemed extravagant. It illustrates the variety which marks the vegetable kingdom, and the work which still remains to be accomplished in the department of botanical discovery and description. Plants divided according to their station, or the physical nature of the locality to which they are adapted, are ranged by De Candolle in fifteen classes, to which two others have been added by M. Bory de Saint Vincent. 1. Maritime or saline plants. These are terrestrial plants which grow on the borders of the sea, or of salt lakes; as salicornia, or saltwort, salsola, or glasswort, which abound on the shores of the Mediterranean, and are there generally burnt for soda, used in the manufacture of glass, especially at Marseilles. 2. Marine plants, as the fuci and many of the alga, which are plentiful in the seas that wash the coasts of Great Britain, and are often attached to stones and rocks near the shore. They are either buried in the ocean, or, situated above low-water mark, are alternately immersed and exposed to the action of the atmosphere; but none of them can be made to vegetate apart from its waters. 3. Aquatic plants, growing in fresh water; as sagittaria, or arrowhead, potamogeton, or pond-weed, nymphæa, or white water-lily. They occupy the beds of rivers, and vegetate in the midst of the running stream or in stagnant pools, being for the most part wholly immersed. The holy kvaμoç, or Pythagorean bean of antiquity, belonged to this genus, and is probably identical with the produce of the Nelumbium, a stately aquatic, common in various parts of the east, especially in China, where the ponds are literally mantled with its leaves and flowers. 4. Marsh or swamp plants, living in ground which is generally submerged, but occasionally dry; as ranunculus aquatilis and sceleratus, or water and celery-leaved crowfoot, polygonum amphibium, or amphibious persicaria. 5. Meadow and pasture plants, as a great number of grasses and trefoils. 6. Plants found in cultivated fields. In this division many plants are included which have been introduced by man along with grain; as centaurea cyanus, corn blue-bottle, sinapis arvensis, or common wild mustard, agrostemma, corn-cockle, several species of veronica, or speedwell, and euphorbia, or spurge. 7. Rock or wall plants; as saxifrages, wall-flower, some species of sisymbrium, or hedge-mustard, bromus, or brome-grass, linaria cymbalaria, or ivy-leaved toadflax. 8. Sand plants, as carex arenaria, or sea-carex, calamagrostis arenaria, or small sandreed, and plantago arenaria, or sand plantain. By the cultivation of these plants, large districts have been reclaimed from utter barrenness, and clothed with stately forests; and countries subject to a periodical invasion of sand, blown over them by the prevalence of certain winds, have been rescued from that calamity—one of the most useful agricultural enterprises of modern times. The plan was first adopted by an engineer of the name of Bremontier, on the coast of Gascony. He sowed, in the driest and most shifting sand, the seeds of the broom, genista scoparia, mixed with those of the sea-pine, pinus maritima, and then covered over the spaces that were sown with branches from the nearest pine forests, by which means the sand was to a certain extent prevented from shifting. The broom, which springs up first, serves the double purpose of further restraining the sand, and of nursing the young pines; and the foliage of the latter, after a growth of seven or eight years under shelter of the broom, becoming annually mingled with the sand, tends to fertilise it. After this period the pine overtops the broom, and frequently entirely kills it with its shade. In ten or twelve years the rising forest is thinned for the manufacture of tar, and for procuring branches to cover the newly-sown districts. After twenty years have passed, a fall of the trees commences for the manufacture of resin. Thus these forests, placed on the dunes or drifting sand-hills between the mouths of the Adour and the Garonne, shelter the whole country behind them from the inroads of the element from the sea, and yield themselves a supply of an important article of commerce. 9. Plants found on rubbish, or those which select the habitations of man and animals, on account of the salts and azotised substances which enter into their composition, as pellitory of the wall, nettles, and some mushrooms. 10. Forest plants, including trees which live in society, as the oak, beech, elm, and fir, and the plants which grow under their shelter, as the greater part of the European orchises. Some of the former attain to enormous dimensions, and survive to a hoar antiquity. Four celebrated yew trees in Great Britain, whose dimensions are on record, appear, from the number of concentric zones observable in a transverse section of their stems, to have lived respectively 1214, 1287, 2558, and 2880 years. In relation to the first of these examples, we have the testimony of history, that this tree was in existence, and must have been of considerable size in the year 1133, it being recorded that the monks took shelter under it during the building of Fountains' Abbey. De Candolle gives the following ages, but is supposed to have overrated them one-third :— The majestic forests of the equatorial zone contain trees of a most gigantic size. On the banks of the Atabapo, a bombax caiba was measured by Humboldt, more than 120 feet high, and 15 feet in diameter; and near the village of Turmero, to the south-west of the city of Cumana, he found the famous Zamang del Guayre, a species of mimosa, with its trunk nearly ten feet thick, and its hemispherical head more than 600 feet in circumference, the branches bending towards the ground in the form of an immense umbrella. The baobabs of Senegal, and of the Cape Verde Islands, exhibit still greater dimensions, several having been noticed with trunks varying from 50 to 100 feet in circumference. 11. Plants of the thickets or hedges, comprehending the small shrubs which form the hedge or thicket, as the hawthorn and sweet brier; the herbaceous plants which grow at the foot of these shrubs, as tuberous moschatel, wood sorrel, and violets; and those which climb among their numerous branches, as bryony, black bryony, and some species of everlasting pea. 12. Subterranean plants, or those which live in mines and caves, entirely excluded from the light, as byssus, truffles, and some other cryptogamic plants. 13. Plants of the mountains, which De Candolle proposes to divide into two sections: 1. Those which grow on alpine mountains, the summits of which are covered with perpetual snow, and where, during the heat of summer, there is a continued and abundant flow of moisture, as numerous saxifrages, gentians, primroses, and rhododendrons. 2. Those inhabiting mountains on which the snow disappears during summer, as several species of snap-dragon, umbelliferous plants chiefly belonging to the genus seseli, or meadow-saxifrage, and labiate plants. 14. Parasitic plants, which derive their nourishment from other vegetables, and which, consequently, may be found in all the preceding situations, as the misletoe, brown-rape, dodder, and a number of lichens, mushrooms, and mosses. 15. Pseudo-parasitic plants, which live upon dead vegetables, or upon the bark of living vegetables, but do not derive their nourishment from them, as epidendron, lichens, and mosses. 16. Plants which vegetate in hot springs, the temperature of which ranges from 80° to 150° of Fahrenheit, as vitex agnus castus, the chaste-tree of the ancients, a species of osier, several cryptogamous plants, and ulva thermalis, the hot-spring laver. 17. Plants which are developed in artificial infusions or liquors, as the mould found in Madeira wine, a species of conferva. This is an arrangement of vegetable tribes, according to the physical nature of the station they occupy, but very different species are found upon similar sites in different parts of the world, a diversity partially referable to a diversity of climate, which we have seen to depend upon elevation and latitude. There are some general laws respecting the distribution of plants, which it is not likely that any subsequent observation will modify. The proportion of the cryptogamic to the phænogamic species, or those which never bear flowers, as mosses and lichens, to the common flowering plants, increases as we recede from the equator. The cryptogamous plants are to the phænogamic, in equatorial countries, as 1 to 5; in Australia, as 2 to 11; in France, as 1 to 2, in several countries nearly equal, and over the whole globe as 1 to 7. The proportion of dicotyledonous plants, or those which have two seed-lobes, like most of the European trees, to the monocotyledonous, which have only one, as grasses, lilies, and palms, increases as we recede from the poles. The absolute number of species, and also the proportion of woody species to the herbaceous, increases as we approach the equator. The number of species, either annual or biennial, is greatest in temperate regions, and diminishes both towards the equator and the poles. The following table gives the relative proportions which several well-defined orders, or families of plants, bear to the whole mass of vegetation in the zones mentioned, and shows the zone in which they occur in the greatest relative abundance. Thus the group of ferns, mosses, lichens, and fungi in the equatorial zone constitutes sth of the vegetation on the plains, and 4th of that on the mountains, while in the temperate zone it forms one half of the whole number of plants, and in the frigid zone almost the entire vegetation belongs to this family. The group of grasses constitutes, in the equatorial zone, 4th of the whole number of plants that exist in it, in the temperate zone th, and in the frigid zoneth, the maximum ratio being attained in the latter. The social plants, or those which live together, covering large tracts of country, like the common heath which is spread over the sand-hills of Jutland, Holstein, Hanover, Westphalia, and Holland, are comparatively rare within the tropics, and are only found on the sea coasts and upon elevated plains. In the cold and inhospitable climate of high northern latitudes, where the ground is frozen hard during nine months in the year, and covered with snow several feet deep, the vegetable tribes are few in number, stunted in their appearance, and of analogous species in the polar regions of Europe, Asia, and America, the continents there being nearly united. Mosses and lichens-the cryptogamia of Linnæus, and acotyledones of Jussieu -form one of the chief botanical features of the arctic zone, and extend in small and isolated tufts as far as travellers have been able to penetrate to the north. One species occurs in great abundance on the southern confines of this zone- the reindeer moss covering of itself a large extent of country, and constituting the principal support of the animal after which it is called, and upon that animal the Laplander entirely depends for his own subsistence. The scurvy grass and sorrel, so valuable for their antiscorbutic qualities, flourish likewise under the almost perpetual snows; and during the short summer which the arctic fields enjoy, some low flowering herbs, the saxifrage, primrose, ranunculus, anemone, and yellow poppy, display their tints upon the sites which have a southern aspect. In receding from the pole, the first specimens of the higher classes of vegetation encountered are a few shrubs of wild thyme, and a species of willow expanding itself laterally to the extent of several feet, yet never rising more than two or three inches from the ground, showing the ungenial influence of the climate. Next comes the "lady of the woods," the birch, but shorn of her fair proportions-a mere dwarf-along with various kinds of bushes yielding edible fruit of delicious flavour, as the cloud-berry and arctic bramble. The latter grows in the wildest and most exposed districts of Lapland. It sometimes offered to Linnæus the only food he could obtain during his perilous journey in that dreary region; and hence the reference made to it in his work:-"I should be ungrateful towards this beneficent plant, which often, when I was almost prostrate with hunger and fatigue, restored me with the vinous nectar of its berries, did I not bestow on it a full description." At the island of Hammerfest, near the North Cape of Europe, in latitude 70° 40′, the birch grows in sheltered hollows between the mountains, attaining to about the human height; and in the low branches which creep along the ground the ptarmigan finds a summer retreat, and breeds in security. The only other trees of any importance, that can maintain an existence within the arctic circle, are some of the pine species, the Scotch and spruce fir, which in Norway pass a short distance beyond its confine, but chiefly the former. Barley is cultivated in this zone as high as latitude 70°; but it requires a favourable aspect and season in order to be ripened, for there is little more than three months between the loosening of the frozen ground and its being again bound up. Wahlenberg states, that the cultivation of this grain succeeds wherever the mean temperature during ninety days rises to 48°. At Enontekeis, in Lapland, barley and turnips yielded nine good crops in the thirty years between 1800 and 1830. The preceding remarks apply to the arctic regions of Europe, which have a less severe climate than those of Asia and America, and, consequently, a more copious vegetation, scanty as it is. Referring to the temperate zone, we find the pine tribe luxuriant at its northern confine, forming the magnificent forests of Scandinavia, where the spruce fir grows perfectly straight, sometimes to the height of two hundred feet. Hence the Germanic name of this tribe, nadel-holz-needle-wood; and Milton's illustration in the splendid description of Satan, "His spear, to equal which the tallest pine The pines occur in much more extensive forests, and with less admixture, than any other genus of timber-trees, immense districts in North America being covered with them; but they do not reach to such high parallels of latitude there, or in Asia, as in Europe. The Norwegian pine is, however, far exceeded by a transatlantic species, Pinus Lambertiana, growing singly on the plains to the west of the Rocky Mountains. Several have been measured, and found to be 250 feet high, 60 feet in circumference at the base, 4 feet in circumference at the height of 190 feet, yielding cones 11 inches round, and from one foot to 16 inches long, a transverse section of the trunk showing 900 annual rings. In descending into the temperate zone, we meet with the alder, aspen, and mountain ash. We then come to the extreme northern boundary of the oak, in latitude 63°, |