1512. When the object in view is the expression of art and design, the propriety of employing species of trees different from those which are natural to, or most abound in, the surrounding country, is obvious. In a country of common pine, the spruce and silver firs and the cedar afford a choice. In a country of oaks or elms, chestnuts, limes, and planes, form suitable contrasts. Where the plantations are extensive, the value of the timber must always be a principal object; and, therefore, the contrasted trees should be chosen accordingly. Some species, however, are so happily adapted for this style, and as ornamental trees in both styles, that they ought seldom to be omitted except near the house: such, for example, as the horsechestnut, lime, sweet chestnut, plane, Turkey oak, cedar, stone pine, &c. As the four last species mentioned are, in exposed situations, liable to injury from extraordinarily severe winters, a few hardier sorts, resembling them in general appearance, should be intermingled in the plantation, to preserve the larger masses in case of accident, but to conform with the general effect in colour and style of foliage, as well as in form. Different species ought not, in general, to be mixed together in the masses; one, or at most two, conforming varieties are sufficient; more would destroy the breadth of colour of the mass, and the character of its surface. Different masses, avenues, and more minute parts, may, however, be planted with different species of trees; rare sorts may be also introduced in lines, along the front of many of the masses, ranged along stars, crosses, &c. The snowdrop tree, for its beautiful blossoms, and the birch and hazel, for the display of their catkins during winter, are well calculated for walks adapted to that season of the year, and should be planted in front of pines, or other evergreens. Such also is the principal situation for flowering shrubs, and no plants can be more showy than the horsechestnut, common lilac, acacia, guelder rose, Portugal laurel, holly, bird-cherry, Pyrus, Mespilus, and laburnum, in similar situations, and for general purposes. In distributing the species of trees in extensive masses, the same general principles of composition must be attended to, which we have pointed out, as far as respects form. The colours and character of the heads of the trees must be connected, and, at the same time, to a certain degree contrasted, in order to produce an artificial and yet harmonious effect.
