558. Biennials are generally classed with perennials in gardening books, because both of them when raised from seeds do not flower till the second year; and though the biennials are said to die after they have ripened their seeds, this is very rarely the case. "Brompton stocks, hollyhocks, wall-flowers, snapdragons, and Canterbury-bells, are generally considered biennials, though tome of them live three or four years. Biennials should he sown in March or April, thinned out in May, and transplanted in September to the place where they are to flower the ensuing year. A little earth should be taken up with the roots, when they are transplanted, and they should be well watered, and shaded for a day or two, till they are thoroughly established. Those kinds which require a peculiar soil, should hare pits prepared for them about a week before they are transplanted, that the earth may have time to settle." (Ladies'Companion to the Flower-Garden, 4th ed.,p. 32.) Hollyhocks should have the pits prepared for them at least a foot square and deep, and they should he filled with a rich soil composed of loam and the remains of an old hotbed.

It would be useless to give lists of biennials, as the genera and species are so few; and the names of the varieties are so innumerable, and so continually changing. As an example of this, in one nursery there are nearly eighty various kinds of snapdragon; and the stocks and hollyhocks are of every shade in their respective colours, from the darkest to the brightest tints. The best way is, when there is time to do so, to visit the nurseries when the plants are in flower, and to procure young plants of the kinds preferred.

559. Perennials, or herbaceous plants, as they are called by gardeners, are those permanent plants which are not woody, but which generally die down to the ground every year, and spring up again the year following. There are some, however, which are called evergreen perennials, which never die down to the ground, such as pinks, carnations, several kinds of saxifrage, etc. Perennials have the great advantage over annuals and biennials, that they do not require renewal from seed, but are propagated by division of the root or cuttings of the stem. The greater part of the plants which ornament the borders of gardens are perennials, including under this term bulbs and tubers. The fibrous-rooted perennials should be taken up and divided when they are growing too large; and even when division on this account is not necessary, most of the kinds are benefited by taking up and replanting in fresh situations occasionally, on the principle of the rotation of crops. Ail plants require certain salts, and other mineral substances which they find in the ground; and when they have taken up all within their reach, which they will do in the course of a few years, the ground in which they grow becomes unfit for them.

Nature has provided a remedy for this by elongating the roots of all perennial plants, whether ligneous or herbaceous, every year; and this is sufficient to prevent trees and shrubs in permanent plantations from being injured; but from the constant digging, etc, in a garden, perennial herbaceous plants are very seldom permitted to extend their roots to a sufficient distance to find suitable soil; and they are, therefore, benefited by taking up and replanting, or laying down decayed leaves or fresh soil over their roots. The season for taking up and replanting perennial plants should be either in autumn, after they have done growing, or in spring, before they begin to grow; and if the soil about the roots looks black and saturated with moisture, or, as gardeners express it, "sour," the roots should be washed quite clean before replanting. Where the roots are to be divided, it may be done, if they are large, with the spade, or, if they are small, with a knife: and, at all events, they should be cut smooth, and trimmed (that is, all the bruised parts removed) with a sharp knife, before replanting. - (See Ladies' Companion to the Flower-Garden, fifth edit, p. 218.)

560. List of ornamental perennial herbaceous plants to be planted in borders. etc.;