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
Fig. 40.—Whorl of leaves of Bedstraw. (Galium vernum.) 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.
CHAPTER VI.
THE ORDER COMPOSITÆ: ILLUSTRATED BY THE SUCCORY, THE SOWTHISTLE, THE DANDELION, THE BURDOCK, THE DAISY, THE CHRYSANTHEMUM, FEVERFEW, PELLITORY OF SPAIN, WILD CHAMOMILE, TRUE CHAMOMILE, YARROW, THE BUR-MARIGOLD, GROUNDSEL, RAGWORT, BIRD’s TONGUE, PURPLE JACOBÆA, CINERARIA, SUNFLOWER, MUTISIA, AND TRIPTILION.
The plants composing the order Compositæ have all compound flowers, which differ from other flowers as much as a compound leaf does from a simple one. As the compound leaf is composed of a number of leaflets or pinnæ united by a common petiole; so a compound flower is composed of a number of florets, united by a common receptacle, which is surrounded by a calyx-like involucre, so as to give the whole mass the appearance of a simple flower. Each floret has a calyx, the tubular part of which is rarely sufficiently distinct to be perceptible, but the limb is generally cut into long feathery segments called pappus. The ovary of each floret contains only one seed; and the fruit, which is called an achenium, retains the pappus when ripe, and falls without opening. There are five stamens, the filaments of which are distinct, but the anthers grow together so as to form a kind of cylinder, through which passes the style, ending in a two-lobed stigma (see a in fig. 41). Most of the corollas are of two