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.
[Illustration: 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 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.
[Illustration: FIG. 37.—SECTION OF THE FLOWER OF RONDELETIA.]
_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.
[Illustration: FIG. 38.—PART OF THE HEAD OF FLOWERS OF RONDELETIA.]
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.
[Illustration: FIG. 39.—COFFEE. (_Coffea Arabica._)]
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.
[Illustration: FIG. 40.—WHORL OF LEAVES OF BEDSTRAW. (_Galium vernum._)]
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.