The American prairies, again, like the meadow-lands of Europe, are alternated with dry, gravelly spaces, marshes, swampy angles, and wooded tracts. It is curious to trace a certain likeness between the genera which inhabit these localities in both continents. Thus, M. Trécul, who explored, in 1848 and 1849, nearly the whole of the State of Missouri to the foot of the Rocky Mountains, Louisiana, Texas, and a part of Northern Mexico, discovered in the vicinity of the Swan's Marsh, Water-Plantains (_Alisma_), Sagittarias, and Nymphæas, in the inundated districts; Characeæ--their tubular branches incrusted with carbonate of lime--bladder-plants, and the beautiful floating Naiadaceæ, in deeper pools and stagnant waters; and the Lythraceæ (or Loose-Strife tribe) on the banks of the brooklets. But the commonest aquatic plant in these morasses, and that which conceals, so to speak, all the other plants proper to such localities, is the _Nelumbium calophyllum_, with its rose-coloured blossoms; its seeds and rhizomes are eaten by the natives. The vast plains of Missouri are sufficiently fertile. Among the plants most abundant in somewhat damp places we must notice several _Compositæ_; the _Liatris_, with their violet flowers and long spiky bunches, the _Calliopsis tinctoria_ of the dyers, the _Gaura_ of Lindheimer, and the _Tripsacum dactyloides_. Asters, Erigerons, Gaillardies, Helianthi (sun-flowers), Solidagos, the _Rudbeckia hirta_, and the _Coreopsis_, are found almost as far south as Texas. By the side of these _Compositæ_ flourish several _Desmodiums_ and _Cassias_, some graceful _Baptisias_--with blue flowers and light green foliage, the _Melanthum Virginicum_, the _Euphorbia marginata_, the _Asclepias Cornuti_--now naturalised in the neighbourhood of Paris--the _Hibiscus palustris_ and _H. moscheutos_, gigantic Malvaceæ, whose splendidly-beautiful flowers are often three or four inches in diameter. As plants widely spread in the stonier Prairies, we may note the Gauras, different varieties of _OEnothera_, and especially the _Silphium laciniatum_ (vulgarly called the Magnetic Plant, or Compass of the Prairies). Its leaves _are said_ to turn their faces uniformly east and west, so that their edges are consequently directed due north and south. The plant is also known as Pilot-weed, Polar-plant, Rosin-weed, and Turpentine-weed; the latter name derived from the copious resin exuded by its stems, which grow to a height of three to six feet, as well as by the leaves, which are deeply pinnatified. In the small woods which skirt the Prairies is found in abundance, twining round the bushes, the _Apios tuberosa_, a leguminous plant formerly recommended to European cultivation on account of the rounded tubercles which grow upon its subterranean stems. The Arabians collect them in the spring, and carefully dry them to eat for food. The Apios belongs to the family of Umbelliferæ, and is consequently allied to celery, parsnip, and carrot.