CHAPTER V.
THE ORDER RUBIACEÆ: ILLUSTRATED BY THE CINCHONA, OR PERUVIAN BARK; LUCULIA GRATISSIMA; CAPE JASMINE; RONDELETIA; COFFEE; IXORA; IPECACUANHA; MADDER; GALIUM; WOODRUFF; AND CRUCINELLA STYLOSA.
This order contains more than two hundred genera; but by far the greater part of these are composed of tropical plants, many of which are not yet introduced into Britain. Several of the genera, on the other hand, are British weeds; and this difference in habit, with others in the qualities of the plants, &c., have occasioned some botanists to divide the order into two: one of the new orders being called Cinchonaceæ, and containing the plants most resembling Cinchona; and the other Galiaceæ, containing the plants most nearly allied to Galium or Bedstraw.
The characteristics of Rubiaceæ, in its most extended sense, are that the ovary is surrounded by the calyx, and placed below the rest of the flower; and that the corolla has a long tube, lined with the dilated receptacle, in which the stamens are inserted. In most of the species, the filaments are very short, and the anthers nearly or entirely hidden in the corolla; and in many cases, the segments of the calyx remain on the ripe fruit, as they do in the genus Pyrus in Rosaceæ, where they form what is called the eye in the apple and pear.
The qualities of the Cinchona division of the Rubiaceæ are generally tonic; but some of the plants, as for example the Ipecacuanha, are used as emetics, and one (Randia dumetorum) is poisonous. The qualities of the Galium division are not so decidedly marked; but the roots of some of the plants are used for dyeing.
THE GENUS CINCHONA, AND ITS ALLIES.
Fig. 36.—Cinchona, Peruvian Bark (Cinchona Lanceolata).
The well-known medicine called Peruvian bark is produced by three species of the genus Cinchona; the pale bark, which is considered the best, being that of C. lanceolata. The flowers of this species are small, and of a very pale pink. The calyx (see a in fig. 36) is bell-shaped, and five-toothed; and the corolla (b) is tubular, with the limb divided into five lobes, and silky within, as shown in the magnified section at c. The stamens (d) have very short filaments, which are inserted in the throat of the corolla. The ovary (e), which is deeply furrowed when young, is inclosed in the calyx; it is two-celled, with a single style, and a two-lobed stigma (f). The capsules retain the lobes of the calyx as a sort of crown (g); and they open naturally at the division between the two cells, as shown at h, beginning at the base. The cells (i) each contain several seeds. C. oblongifolia, which yields the red bark of the shops, has cream-coloured flowers, as large as those of a Jasmine, which they resemble in shape; and C. cordifolia, which produces the yellow bark, has flowers like the first species, and heart-shaped leaves. The singular plant called Hillia longiflora, is nearly allied to Cinchona; as is also the beautiful and delightfully fragrant Luculia gratissima. In this last plant the tube of the calyx is very short, and pear-shaped, and the segments of the limb are short, and sharply pointed. The corolla is salver-shaped, with a long tube, and a spreading, five-parted limb. The anthers are nearly sessile, and the short filaments to which they are at tached are inserted in the throat of the corolla, only the tips of the anthers being visible. The stigma is divided into two fleshy lobes, and the capsule splits, not like that of Cinchona, but from the apex to the base in the centre of each cell. The seeds are very small, and each has a toothed, membranous wing. The flowers of this beautiful plant are produced in a large head, and at first sight greatly resemble those of a Hydrangea; but they are easily distinguished by their delightful fragrance.