placentæ, their margination, and the position of the cotyledon within the seed. The greater portion of these nine tribes have their species generally diffused, some on the western side of the Rocky Mountains, others on the eastern plateau, and the Atlantic board. The tribe Isatidere is an exception, however, as it appears only in the far west, where six or seven species of Thysanocarpi oceur.

Commencing with the ARABIDEE, the first tribe of the great siliquose division, we have three species of Cheiranthus in North America. The C. capitatus in California and Oregon, passing into British territory from Puget Sound, the C. Pallasii on the North West coast, and the C. Hesperidoides, in Pensylvania, Kentucky, Illinois and Arkansas. No locality in the British territories eastward of the Mountain, appears to be quoted by any author for American Wallflowers; and certainly I have not heard of them native in Canada. The fragrant and most grateful, the Cheiranthus cheiri, is only to be found in our gardens.

The Nasturtiums (Water-cresses) are well sprinkled over the country south of Canada, but more rarely elsewhere. We possess the N. palustre, however, in all quarters, wherever the ground is suitable for it, throughout the length and breadth of the land. The N. natans, a scarcer plant, is to be found in Canada and the United States, along the borders of small lakes, and may be distinguished by its immersed leaves being manyparted with capillary segments. The other Nasturtiums are distributed to the number of five in the United States, and of four in the Oregon and on the north west coast.

Barbarea præcor attains to a high latitude, say 68°, and we have it also along the banks of rivers in Canada. The Barbarea vulgaris, common in the Northern States, is also found in Oregon and on the north-west coast, running north to Sitka, within the Russian territories. There may be difference of opinion, whether this be an introduced plant or not, according to the quarter where it may be found. Occurring in settled districts in the States, one might pronounce it introduced, while in new or wilder situations another would at once say it was indigenous. It is the Yellow Rocket and Winter Cress of the English; the Cresse de Terre of the French; and Hierba de Santa Barbara of the Spanish.

Passing over the genus Streptanthus, of which three species occur in the United States, three in the rocky mountains, and six in California and Oregon, we arrive at the Turritis of Dillenius.

Of this genus the species most frequently seen is the T. glabra, common enough on the shores of Lake Superior and the banks of the streams running into Hudson's Bay; it extends northward as far as lat. 64°, and in the more northern latitudes is accompanied by the T. patula, and T. retrofracta, which are distinguished principally by their spreading and retrofract pods. Within the arctic circle the T. mollis and T. diffusa are joined to them, when the T. retrofracta drops off. The T. patula, although not reported as higher than 68° on the continent, has nevertheless a variety in Greenland, from which country Sir W. J. Hooker has received it. The Turritis macrocarpa and T. striata are western plants; the T. brachycarpa is confined to the Michigan territory.

The genus Arabis has 15 species now discovered in North America, of which five are natives of this province, the A. petræa, hirsuta, lyrata, lævigata, and Canadensis. The A. hirsuta, frequent near the coast of Hudson's Bay, extends to the Oregon, and along the shores of the Pacific as far as Sitka. The A. petræa is also marked by Chamisso as a plant of Unalashka. On the north shores of the St. Lawrence below Quebec, the A. lævigata is common, and is met with here and there throughout Canada. The two other Canadian species, the A. lyrata and Canadensis, like the last, travel southwards, and are seen scattered over the States as far as Virginia, Georgia, and the Arkansas. Two species, which appear to be confined to Labrador, the 1. Alpina and A. striata, are amongst the cruciferæ of Europe. Of this rather extensive genus there are still 7 or 8 species to be found in North America, but to the southward of the boundary line. Four of these are the discovery of the indefatigable Nuttall amongst the Rocky Mountains and towards the Oregon.

The bitter cresses, or Cardamines, not so numerous in species as the last genus, and more seldom met with in the north than the genera, Turritis and Arabis have the leaves generally pinnately divided, which is a form little observed in the other two. Cardamine rotundifolia, and C. bellidifolia, have undivided leaves, and are extensively distributed, each in its chosen habitat. The former best known in the eastern and northern states, was also procured by Drummond in the Rocky Mountain defiles, from lat. 52° to 57, which for one season, the summer of 1856, he took as the range for his botanical researches. Lake Superior and Hudson's Bay have also been quoted as affording this plant. The C. bellidifolia is a native of Arctic America, but, like some other plants of

that region, has its alpine residences in more southern latitudes. The summits of the Rocky Mountains in lat. 52°, and what is more remarkable and interesting, the White Mountains of New Hampshire, claim the C. bellidifolia as a native. Sub Jove frigido! we may exclaim, as we meet this errant stranger in its airy quarters, and imagine while we pluck it that we inhale the atmosphere of the arctic zone. A still more extraordinary place allotted for this plant is California, as testified by Douglas, whose observations were always so clear and so well authenticated, that we are scarcely at liberty to doubt them. The pinnately leaved Cardamineæ amount to seven, according to Torrey and Gray, three of which are Arctic plants. The C. pratensis of Linnæus is on the islands of the Arctic Ocean as well as in Behrings Straits, so that we may conclude with a considerable degree of certainty that it extends alongst the whole northern coast of this continent. Being a native also of Hudson's Bay, Canada, and the western part of the State of New York, it would appear that it accommodates itself to a breadth of climate equivalent to at least 30 degrees of latitude. The C. hirsuta, running less to the northward, (as far as has yet been observed,) is nevertheless found on the coasts bordering on the Arctic Sea, and on the north-west coast in high latitudes, having a distribution eastward and westward equal to the breadth of the continent in lat. 45°. The C. Virginica of U. States' botanists is a variation of the Cardamine we have just had under consideration. The Cardamine digitata is confined entirely to the north, and passes over Behring's Straits to form one of the Siberian Flora. Other three species are the C. angulata, and C. oligosperma, from the Oregon, and C. Ludoviciana, from Georgia, Kentucky, and the Arkansas, but they are foreign to the British possessions. Cardamine purpurea is a Siberian plant, and although by the celebrated voyage and discoveries of Captain, now Admiral Beechey, we know that it passes over to Kotzebue's Sound, yet it must still only be considered as foreign, as it has not yet been heard of beyond the Russian territories.

The Dentaria, near Cardamine, but having the roots toothed or tubercled, is a southern genus. D. laciniata, and D. diphylla, enter Canada, but do not, as far as I have observed, advance farther northward. The D. tenella, and D. macro-carpa, belong to the Oregon, and it is very probable may yet be discovered passing the boundary line of 49°, and so enter into our list of New Caledonia or Fraser River plants. Should Palliser's party cross

the Rocky Mountains, much information no doubt will be obtained regarding plants, and other subjects of natural history, from the able and zealous naturalists composing that scientific party. The Thompson's and Frazer's River countries display as fine a fie'd for the enterprise of scientific and speculative minds as is to be found in North America.

Following the Dentaria, we have the genus Parrya, a name given by R. Brown to an Arctic plant or two, to commemorate the distinguished officer, who was amongst the foremost of the discoverers in the expeditions which were set on foot during the present century, to ascertain the reality of a North West passage. As it is a northern plant, I may state that in it the pods are broader than in the genera hitherto mentioned, the valves are veiny, the seeds broadly margined, and the funiculi more or less adherent to the septum. On the Arctic coast, to the eastward of Mackenzie River, we have one species, the Parrya arctica of Brown; and to the westward of the same river, and on the northwest coast, the Parrya macrocarpa. By the late Sir John Franklin and his companion, now Sir George Back, the P. macrocarpa was brought home on their second voyage to and from the Arctic coast; but it must have been known before this to the Russians, Linnæus having described a variety of it under the name, Arabis caule-nudo.

them

The two genera with which Torrey closes the Arabidea of North America are the Phenicaulis and Leavenworthia; but I pass over, as the former occurs only to the westward of the Rocky Mountains, at the Forks of Lewis and Clark, on the high hills of the Wallawalla, and the other is confined to the Central and Southern States.

We are introduced to the tribe Sisymbrea in the genus Hesperis, of which there are two of North America. The Hesperis minima is the same plant as the H. pygmæa of Hooker, and probably does not differ from the Cherianthus Pallasii of Pursh. It scarcely passes to the southward of the Arctic circle, but stretches from Behring's Straits eastward as far as Great Bear's Lake, where it was found by Sir John Richardson. The H. Menziesii is recognized as coming only from California.

The genus Sisymbrium, like that of Arabis, dispenses itsspecies over Arctic as well as Sub-arctic America, and that too in not very unequal order. The Sisymbrium officinale is supposed to have been introduced from Europe into Canada and the

United States, but the S. Sophia, which appears in various localities in Lower Canada, may be a native; a point, however, not easy to be determined. Common to British America and the United States is the very generally diffused Sisymbrium canescens, which is also found on the Rocky Mountains, and westward to Oregon and California. This soft-looking, frequently hoary plant, is very hardy, bearing the rigours of the north as well as the heats of Georgia and Arkansas. The S. Sophioides of Fischer, found in high latitudes, extends from Hudson's Bay to the Arctic coast, stretching westward round the continent to the Pacific. It is remarkable amongst its kind by the flowers and pods being in umbelliform corymbs. The S. junceum is from dry stony grounds in the Oregon. Six or seven other species, the discoveries of Nuttall, are found on the hills of the great dividing ridge, south of 49; but it is very probable that some if not all of these will be met with by Monsieur Bourgeau, the French botanist attached to Palliser's exploring party, which has been busy last season on the Bow River, and near the boundary line, where it crosses the back-bone of America. In that quarter, hitherto so dangerous, and therefore seldom or never approached by the foot of civilized man, there is a portion of both prairie and mountain yet unsearched, its geology and its botany only deducible from what is known of districts far removed from it. We may therefore anticipate a most interesting description of novelties, in the natural history of the region in question, when the surveying and exploring expeditions bring the fruits of their labors before the public. In concluding my remarks on the present genus, I may observe that the S. humile, a Siberian species, is also a production of the Rocky Mountains, but in the higher latitudes, from 52° to 68°. The Sisymbrium Thalianum, the Arabis Thaliana of Linnæus, has been introduced from Europe.

Passing the Tropidocarpa of Hooker, natives of California, we come upon the genus Erysimum, which contains some handsome species, shewing themselves on the plains, and on the dry grassy spots throughout the north. The E. cheiranthoides, known in Europe, is also gathered in Canada and the United States, and in the prairie country. We find it west of the Rocky Mountains in lat. 47°, as far as the Pacific; and Hooker gives it a place on the banks of the McKenzie, up to 67o. The E lanceolatum, a handsome little plant, appears in the flora of Canada, and, proceeding northwards, reaches the Arctic Sea.