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.

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 attached 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.

_Manettia cordifolia_, a very pretty stove-twiner often seen in collections, is very nearly allied to Luculia, differing principally in the shape of the flowers, which in Manettia have a long tube and a very small limb. _Bouvardia triphylla_ and the other species of Bouvardia, and _Pinckneya pubescens_, belong to this division; and such of my readers as have the living plants to refer to, will find it both interesting and instructive to dissect them and compare the parts of their flowers with the description I have given of Luculia and Cinchona, so as to discover the difference between the different genera; afterwards reading the generic character of each given in botanical works, that they may see how far they were right.

THE GENUS GARDENIA AND ITS ALLIES.

The Cape Jasmine (_Gardenia radicans_) is a well-known greenhouse plant, remarkable for the heavy fragrance of its large white flowers, which die off a pale yellow, or buff. The calyx has a ribbed tube, and the limb is parted into long awl-shaped segments. The corolla is salver-shaped, that is, it has a long tube and a spreading limb, the limb being twisted in the bud. There are from five to nine anthers, having very short filaments which are inserted in the throat of the corolla. The stigma is divided into two erect fleshy lobes. The ovary is one-celled, but there are some traces of membranes, which would, if perfect, have divided it into from two to five cells. The seeds are numerous and very small. _Gardenia radicans_ is a dwarf plant, which flowers freely when of very small size, and is easily propagated from the readiness with which its stem throws out roots; but _G. florida_ is a shrub five or six feet high, and much more difficult to cultivate. In both species the flowers are generally double, and the petals are of a fleshy substance, which gives the corolla a peculiarly wax-like appearance.

There are many other species, but the two above-mentioned are the most common in British gardens. _Burchellia capensis_ is generally considered to belong to this division of Rubiaceæ, though its flowers bear more resemblance to those of Cinchona; and the singular plant called _Mussæuda pubescens_, the flowers of which are small and yellow, but the bracts are so large and so brilliantly white as to look like flowers; _Posoqueria versicolor_, an ornamental plant lately introduced, belong to this division.

THE GENUS RONDELETIA AND ITS ALLIES.

_Rondeletia odorata_, sometimes called _R. coccinea_, and sometimes _R. speciosa_, is a very fragrant stove shrub, a native of Cuba. The flowers are produced in corymbs, and their botanical construction is shown in the magnified section _fig._ 37. In this _a_ is the ovary inclosed in a hairy calyx; _b_ shows the limb of the calyx cut into awl-shaped segments; _c_ shows the manner in which the very short filaments of the anthers are inserted in the throat of the corolla; _d_ shows the termination of the dilated receptacle which lines the tube of the corolla; and _e_ the segments of the limb. I have given the section of this flower, that my readers may compare it with the section of the flower of the Cinchona in _fig._ 36, in p. 87, and may see the general resemblance which connects the two plants in the same order, and the differences which mark them to be of different genera. _Fig._ 38 is a tuft of flowers of _Rondeletia odorata_. _Wendlandia_ is nearly allied to Rondeletia; as is the magnificent _Portlandia grandiflora_, which somewhat resembles _Brugmansia lutea_ in shape though not in colour, as its flowers are white.

THE GENUS COFFEA AND ITS ALLIES.

The Coffee-tree (_Coffea arabica_) differs from the other Rubiaceæ in the tube of its calyx being very short and disappearing when the ovary begins to swell; and in the filaments of the stamens being sufficiently long to allow the anthers to be seen above the throat of the corolla (see _a_ in _fig._ 39). The limb of the corolla (_b_) is five-cleft, and the style (_c_) bifid. Each ovary when its flower falls, becomes distended into a berry (_d_) or rather drupe, containing the nut _e_, in which are two seeds, flat on one side, and convex on the other, which are placed with the flat sides together, as shown at _f_; each seed having a deep longitudinal groove, as shown at _g_. These seeds are our coffee.

The flowers of _Ixora coccinea_ have the same general construction as those of the other plants of the order. The calyx has an ovate tube, and a very small four-toothed limb; and the corolla is salver-shaped, with a long and very slender tube, and a four-parted spreading limb. There are four anthers inserted in the throat of the tube of the corolla, and just appearing beyond it, and rising a little above them is the point of the style with its two-cleft stigma. The berry is two-celled, but it differs from that of the coffee in retaining the lobes of the calyx, which form a sort of crown. There are many kinds of Ixora, all stove shrubs, and all conspicuous for their large heads or rather corymbs of showy flowers. The genus Pavetta has been divided from Ixora, principally because the species composing it have the style projecting considerably beyond the corolla, instead of only just appearing above it.

The drug called Ipecacuanha is the produce of two plants belonging to this order, _Cephælis Ipecacuanha_ and _Richardsonia scabra_; though a spurious kind is made from the roots of three species of Viola, all natives of South America, and a still inferior one from the roots of a kind of Euphorbia, a native of Virginia and Carolina. It is important to know this, as the best kinds possess tonic properties as well as emetic ones, while the inferior kinds are only emetics, and they are very injurious if taken frequently. The best brown Ipecacuanha is the powdered root of _Cephælis Ipecacuanha_; a plant with small white flowers collected into a globose head, which is shrouded in an involucre closely resembling a common calyx. The true calyx to each separate flower is small and roundish, with a very short five-toothed limb. The corolla is funnel-shaped, with five small bluntish lobes. The anthers are inclosed in the corolla, and the stigma, which is two-cleft, projects only a little beyond them. The berries are two-celled and two-seeded, and they retain the lobes of the calyx. The root is fleshy and creeping. _Richardsonia scabra_, which produces the white Ipecacuanha, has its flowers also in heads, but the calyx is larger in proportion to the corolla, and the stamens and style are both visible. The capsule contains three or four one-seeded nuts, crowned by the calyx; which, however, becomes loosened at the base, and falls off, before the seeds are quite ripe. Cephalanthus, Spermacoce, and Crusea, are nearly allied to Richardsonia.

The above plants all agree, more or less, with Cinchona, in their qualities, and they are all included by Dr. Lindley in the order Cinchonaceæ.

THE GENUS GALIUM AND ITS ALLIES.

The common Bedstraw (_Galium vernum_) is a British weed, common in dry fields and on little knolls, which produces its cluster of bright yellow flowers in July and August. The flowers are so small that it is difficult to examine them in detail, but, by the aid of a microscope, the ovary will be found to be inclosed in the tube of the calyx as in the other Rubiaceæ, though the calyx has hardly any limb. The corolla is what is called rotate or wheel-shaped, and its limb is divided into four segments. There are four short stamens, with their filaments inserted in the throat of the corolla, and two very short styles. The fruit is a dry capsule inclosing two seeds. Thus far the construction of the plant agrees with the other Rubiaceæ, but the stem is square, and the leaves are different, for they are without footstalks, and are disposed in what is called a whorl (see _fig._ 40). The whorl, however, according to Professor De Candolle, does not consist entirely of leaves; but of two opposite leaves and two or more stipules, which are so like the leaves as scarcely to be distinguished from them, though upon close examination, it will be found that the leaves have buds in their axils (that is between them and the stem), which the stipules have not. This theory is not adopted by Dr. Lindley, who considers the whorl to consist entirely of leaves, and to be one of the distinctive marks of his order Galiaceæ.

All the plants in this division of Rubiaceæ agree with the common Bedstraw (_Galium vernum_) in the formation of their leaves and stem; but the species of Galium are distinguished by the margins of the leaves and the principal veins, in nearly all the species, being covered with prickles, which in some cases point forwards, and in others are bent back, so as to catch everything they touch. This is particularly the case with the leaves of the plant called Goose-grass, or Cleavers (_Galium aparine_); and its fruit is covered with hooked bristles, which take so firm a hold as to make it difficult to separate them from anything they have caught hold of. The pretty little weed called Field Madder (_Sherardia arvensis_), the fragrant Woodruff, (_Asperula odorata_), and _Rubia peregrina_, the only British species of Madder, all agree with Galium in its more important characters; and as they are all common weeds, my readers will probably find it interesting to trace the differences between them. Galium and Rubia agree in having scarcely any limb to the calyx, and a rotate corolla; but the limb, which is only four-parted, or even three-parted, in Galium, has always five lobes in Rubia; there are also five stamens in Rubia, and the fruit is a berry; whereas there are only four stamens in Galium, and the fruit is dry. Sherardia agrees with Asperula in having a funnel-shaped corolla with a four-cleft limb; but in Sherardia the limb of the calyx remains on as a crown to the fruit, while in Asperula it drops off. In Sherardia there is only one style with a two-lobed stigma; and in Asperula there are two styles united at the base.

There is a very pretty plant called _Crucinella stylosa_, which has lately been much cultivated in gardens, and which belongs to this order. This plant has large heads of pretty pink flowers, each of which has a funnel-shaped corolla, with a long tube concealing the anthers, but beyond which the style projects so far as to give rise to the specific name of _stylosa_. The stigma in this plant is clavate, that is, club-shaped, and it is cleft in two, though the lobes are not spreading.