region now famous as the Garden of the Gods.—ED. [150] A. _cœrulea_, JAMES.—Leaves twice ternate; flowers terminal, remote, nectaries strait and very long. It inhabits shady woods of pine and spruce within the mountains, rising sometimes to the height of three feet. In passing from the headwaters of the branch of the Platte, called Defile creek, to those of one of the northern tributaries of the Arkansa, we noticed some change in the soil, and soon met with many plants we had not before seen. Several of these, as the common juniper and the red cedar, (Juniperus _virginiana_, Ph.) the black and hemlock-spruce, (Abies _nigra_ and A. _canadensis_) the red maple (Acer rubrum, Mx.) the hop horn-beam (Ostrya Virginica, L.) the Populus _tremuloides_, Mx. Pinus _resinosa_, Pyrola _secunda_, Orchis _dilatata_, olc. are common to mountainous districts in all the northern parts of the territory of the United States; many others are here found, which require more careful and extensive comparison with the plants of Mexico, Siberia, and other countries, than have yet had the opportunity to make.—JAMES. One of these singular hills, of which Mr. Seymour has preserved a sketch, was called the Castle Rock, on account of its striking resemblance to a work of art. It has columns, and porticoes and arches, and {205} when seen from a distance has an astonishingly regular and artificial appearance. July 12th. [10th and 11th cont'd.]. On approaching it, the base is found enveloped in an extensive accumulation of soil, intermixed with fragments of rapidly disintegrating sandstone. The lower portions of the perpendicular sides of the rock are of loosely cemented pudding-stone, but the summit is capped by a compact and somewhat durable sand-rock. This is surmounted by a scanty soil, in which are a few stinted oaks and junipers. We had seen no bisons for several days, but in the afternoon a few were discovered at a distance from our course, and three men despatched in pursuit of them. They were grazing on the side of a hill near a mile distant. As provisions were growing scarce with us, we watched the progress of the hunters with some anxiety. At length the firing commenced, and we enjoyed a distant, though distinct view of the animating spectacle of a bison hunt. In a short time the hunters joined us with their horses loaded with meat. We halted to dine on the tributary of the Arkansa before mentioned, nearly opposite the Castle Rock. Intermixed with the grass upon which we sat down to our dinner, we observed a small campanula, with a solitary terminal flower, about as large as that of the common hare-bell (C. decipiens). This species we believe to be identical with the C. uniflora of Europe, which has not been heretofore noticed in the United States.