ORDER XVII.—FLACOURTIANEÆ.
The plants belonging to this order are mostly Indian plants, little known in Europe.
ORDER XVIII.—BIXINEÆ.—THE ARNOTTA TRIBE.
Bixa Orellana is a shrub, a native of South America, which requires a bark stove in England. It has pink flowers with five petals, and a green calyx of as many sepals. The stamens are numerous; but they are on rather short filaments. The leaves are very large and heart-shaped. The fruit is a berry, and the pulp in which the seeds are immersed, when dry, is the Arnotta used in colouring cheese.
ORDER XIX.—CISTINEÆ.—THE CISTUS TRIBE.
There are only four genera in this order, viz., Cistus, Helianthemum, Hudsonia, and Lechea; and though there are almost innumerable plants comprised in it, they nearly all belong to the first two.
All the plants belonging to the genera Cistus, the Rock-rose, and Helianthemum, the Sun-rose, have showy flowers, each having five petals, which are crumpled in the bud like those of the Poppy; they also resemble the petals of the Poppy tribe in falling almost as soon as they have expanded, as every one must have observed who has noticed the flowers of a Gum-Cistus. The calyx in both Cistus and Helianthemum generally consists of five sepals, two of which are larger and of a paler green than the others, and grow a little below them; and this calyx remains on after the petals have fallen, and, indeed, till the seed is ripe. In the Gum-Cistus, however, and some other species, the two outer sepals are wanting. There are a great many stamens, which are rather short, and form a tuft in the centre of the flower, surrounding the pistil, which has a round flat-headed stigma, a rather long style, and an ovary divided into five cells. The seeds are numerous, and each has a separate footstalk, by which it is attached to the placentas, which, in the Cistus tribe, are in the centre of the ovary, and not proceeding from its sides, as in the Mignonette. The capsule, which remains covered with the calyx till it is quite ripe, divides into five or ten concave valves, each having a placenta, to which the seeds were attached, in its centre. The seed of any plant belonging to the order Cistaceæ, is remarkable when cut open for the great size of the embryo enclosed in it, and the curious manner in which it is curled up. The embryo is the germ of the future plant, and it is usually buried in a great mass of albumen, or floury matter intended for the nourishment of the young plant, till its roots are in a fit state to supply it with nourishment. In the seed of the Cistus, there is scarcely any albumen; but in its stead a long narrow embryo, coiled up like a sleeping snake.