RELATIONS. This region is so rich in variety that very extensive relations might be expected, but though these are certainly numerous, the peculiarity of its flora is very striking. With Europe it might be supposed to have many species in common; yet of 2,891 phanerogamic, only 385 re-appear there. The proportionate scarcity of umbelliferæ, cruciferæ, and trifolium, is somewhat remarkable; and in examining the vegetation we cannot fail to be impressed how closely the productions of cold and hot regions are brought together, and consequently how much the intermediate temperate portion is compressed. This appears to be the reason why the groups just mentioned are so little seen. With the China region there are some interesting points of resemblance, through hydrangea, cocculus, and others; with South Africa in amaryllideæ, India in scitamineæ; and with the Patagonia and California regions through berberis, and many other genera with the latter. Clusia rosea is met with in Carolina, and several cinchonacea prevail through the region to the vicinity of the lakes.

V.-THE CALIFORNIA REGION.

EXTENT. After crossing the Columbia river from the north, an entirely altered vegetation commences. The dense compact forests of abies cease suddenly, and are supplanted by an open country, spotted by occasional clump of oaks, and the river lines fringed by platanus, fraxinus, juglans, and salix. The outline of the region may

botany of the United States, as in the American edition of Murray's Encyclopædia of Geography.

be traced up the Columbia river to the Rocky Mountains, which it meets in about 50° N. latitude, and is continued along them to the south, till approaching the commencing waters of the Colorado, it runs along its course to the gulf of California. The remaining portion is circumscribed by the Pacific Ocean.

PHYSICAL CHARACTERS.-In its northern part the surface is regular, and there are some well-watered fine alluvial plains, without a rock or stone. Occasionally ranges of low mountains traverse it, chiefly of porphyry, basalt, and jasper, which are not of sufficient elevation to affect materially the vegetation, but support some groves of pinus lambertiana and abies religiosa; pinus rigida prefers the plains. The broad plains which separate them are often overflowed in the winter, which with their deep rich soil renders them very fertile. To the south, the scenery is wild and rugged, nearly altogether mountainous, the ranges running from north to south. Not a tree is to be seen, but there is a moderate sprinkling of a more lowly and interesting vegetation. The prevailing rocks here are serpentine, gneiss, basalt, and greenstone. There is no soil nor fertilizing streams, water being very

scarce.

CLIMATE.-To the north the climate is even and temperate; the winters are mild and of short duration, and snow appears on the loftier hills; and the summers have an agreeable warmth, with the atmosphere clear and transparent. In the autumn the dews are excessively heavy. The summers of the southern portion are warmer, the temperature being generally from 60° to 74o. The rains are soon over, but during their continuance deluge the country. The atmosphere is particularly clear, and it would also appear dry, as when signs of the

wet season were gathering in the heavens, the dew-point was 62o, the shade 72°; and at the same time the sun's rays were 115o.

FLORA. The finest part of this region is to the north, where an open country prevails, varied by patches of trees of noble growth. Of the oaks, two species are deciduous, and two evergreen. The latter are confined to the neighbourhood of the sea coast between 38° and 34° N. latitude. The other trees are not numerous, and are chiefly comprised under platanus, acer, pavia, juglans, cornus, laurus regia, and the aromatic tetranthera californica. It is among these forest trees that the chief relations with the Iroquois region is established, and it is one of affinity. The undergrowth consists of several species of rubus, ribes, lupinus, rhus, vaccinium, arbutus, and lonicera; and such is the variety of some of these, that a new species may be met with almost every hundred miles. Vitis, scarcely expected, grows abundantly on the margins of some of the rivers. Shrubby compositæ prevail throughout, but are in the greatest intensity towards the centre of the region; and in the more arid parts cacteæ and euphorbiaceæ are particularly numerous, with a few leguminosa. Cacteæ are not seen further north than 34°; here also is the limit of ricinus communis, of course introduced, as is phoenix dactylifera, a few large trees of which may be seen about San Diego, but only yielding a sour fruit.

As characteristic peculiarities of the region may be mentioned, its great aridity, general scarcity of trees, superior prevalence of cacteæ, compositæ, and euphorbiaceæ, great number of plants with lactescent juices, and with fragrant foliage, the frequent developement of the flowers and leaves at different periods, and the general small range of its species. The negative features consist

in the scarcity of ferns, mosses, and fungi, none of which exist in the southern part, except perhaps the latter during the rains. Lichens, with sickly aspects, occasionally cling to the trees or rocks.

RELATIONS.-California, though less known, has an equally fine climate with the south of Europe, Chili, the Cape of Good Hope, or New South Wales; and with these parts of the world has a general resemblance in its vegetation. In establishing a comparison between the western and eastern parts of the American continent, a superiority must be assigned in the forest trees to the east, and in the herbaceous vegetation to the west.

VI. THE PRAIRIE REGION.

EXTENT. This is a peculiar tract enclosed by the vast forests of North America. It extends from within a hundred miles of the west bank of the Mississippi to the Rocky Mountains, stretching to 54° N. latitude, and again only bounded on the south by the wooded country of the Texas and the Mexican Sea. The outline is tolerably regular, except that two processes cross the above river; one penetrating the states of Illinois, Indiana, and Ohio; and the other farther south, stretching into Alabama.

PHYSICAL CHARACTERS.-The prairie is far from being a continuous extensive plain, and in this respect must yield to the Pampas. It consists rather of an assemblage of plains, often with slightly undulating surfaces, and frequently covered with a fruitful soil; their level being occasionally broken by projecting masses of rocks or ranges of low hills. The subjacent structure is composed of red or grey saliferous sandstone, chiefly the

former, with beds of clay. Chloride of sodium abounds with other salts, and are found largely in the vicinity of the Rocky Mountains, and in the northern part of the region. Gypsum likewise occurs, and gravel, sand, or boulders occasionally prevail.

CLIMATE. The long droughts to which the prairie is liable have been supposed to preclude the existence of shrubs or trees, and to be favourable to the more fugacious grasses. Heavy rains sometimes fall, and during their continuance rivers spring up, and gliding over the country, nourish a lively vegetation. In the dry season these soon shrink to small streams, disconnected chains of ponds or marshes, or entirely disappear.

FLORA. This extensive portion of country supports a by no means insignificant flora. Gramineæ is the most important group, and is represented by numerous festuca, bromus, stipa, aristida, poa, agrostis, crypsis, kæleria, hordeum, eriocoma, and others. Grasses flourish more particularly in the northern part, yielding gradually towards the south to various herbaceous compositæ, some cucurbitaceæ, vites, scrophularineæ, solaneæ, boragineæ, and euphorbiaceae. The peculiarities of the region are derived chiefly from the absence of trees, the great preponderance of gramineæ and of composite through the genera rudbeckia, helianthus, silphium, coreopsis, and other allied groups, and in the scarcity of bulbous plants in a situation, where, from a comparison with the Cape of Good Hope and other places, they might be supposed to exist. Cacteæ appear farther north in the prairie than in the California region, and are often accompanied in both by a yucca.

However interesting the Rocky Mountains may prove to the geologist, they have no flora sufficient to give them any individuality as a region. They are as destitute of