The order Linaceæ is a very small one; and, indeed, it consists principally of the genus Linum. The Flax was formerly included in the Caryophyllaceæ, which it resembles in having five petals, five sepals, and five stamens; but it also resembles the Mallow in its capsules, and in its stamens growing together at the base; and the Cistus in its persistent calyx, and the disposition of its sepals. These links, which connect one order with another, and make them appear alike but not the same, form, I think, one of the most interesting parts of the Natural System. We are led on from one gradation to another, by scarcely perceptible shades of difference through the vegetable kingdom; and, indeed, through the whole system of creation: the beautiful harmony, and unity of design, visible throughout, bearing the strong impress of the Divinity whose power has made the whole. The common Flax (_Linum usitatissimum_), though in its appearance only an insignificant weed, is a plant of great benefit to man. The fibres of the stem are used to make linen, and the seeds (linseed) are crushed for oil. The flowers are blue, and have five regularly-shaped petals, which are twisted in the bud; and a distinct calyx of five pointed sepals, two of which grow from a little below the others, as in the Gum Cistus; and, as in that plant, the calyx remains on till the seeds are ripe. There are five stamens, the filaments of which grow together slightly at the base, and there are five little points like filaments without anthers, rising between the stamens. The petals are connected with the ring formed by the united filaments, and sometimes the petals themselves grow slightly together at the base. The capsule consists of five two-celled carpels, grown together; each cell containing one seed, and each carpel terminating in a rather slender style, tipped with a ball-like stigma. When ripe, the capsule opens naturally, by dividing into ten valves, to discharge the seeds; which are flat and shining, with a large embryo. These seeds are called Linseed in the shops, from Linum, the botanical name of the plant; and, as is well known, they are not only used for various purposes, but oil is expressed from them. The stem of the common Flax, though it is only an annual, consists of woody fibre, like that of a tree in its young state; and it is this fibrous part that makes the yarn for thread, after it has been separated from the fleshy part, by steeping the stems for a long time in water. The perennial Flax (_Linum perenne_), which, as its name imports, lasts several years, differs in little else from the common kind, except that its sepals are obtuse, and its leaves are much smaller and narrower. Both these are natives of Britain. There are many other species, some of which have yellow flowers. ORDER XXVIII.—MALVACEÆ.—THE MALLOW TRIBE. FIG. 119.—THE FLOWER, STAMENS, AND PISTILS OF THE ALTHÆA FRUTEX.