_Quassia amara_, the bark of which is sometimes used as a substitute for hops, is perhaps the best known plant belonging to this order. All the species are trees or shrubs, natives of tropical America, with bitter bark, milky juice, and pinnated leaves. ORDER LVII.—OCHNACEÆ. Tropical shrubs with yellow flowers and shining leaves; seldom seen in British hothouses. ORDER LVIII.—CORIAREÆ. Only one species of this order is common in British gardens, viz. _Coriaria myrtifolia_; the leaves of which are astringent, and used in dyeing black, and the berries are poisonous. § II.—Calycifloræ. The plants comprised in this division have their petals and stamens inserted in the calyx, or in a lining of it formed by the dilated receptacle. ORDER LIX.—CELASTRINEÆ. [Illustration: FIG. 135.—THE HOLLY.] This order is divided into three sections, each containing well-known plants. The first of these takes its name from _Staphylæa pinnata_, the Bladder-nut. In the flowers of this plant the calyx is in five divisions, and white tinged with pink, so as to be scarcely distinguishable from the corolla. There are two or three carpels, which are surrounded by the receptacle, and the styles of which adhere slightly together. The capsule is bladdery, and consists of two or three cells, each containing one smooth, brownish, bony seed, which looks as though one end had been cut off at the hilum. The leaves are compound, each having five leaflets. The second section contains, among other plants, the Spindle-tree (_Euonymus europæus_), Cassine, and the Staff tree (_Celastrus scandens_). The Euonymus has small whitish-green inconspicuous flowers; but it is remarkable for the beauty of its capsules, which are fleshy, and of a bright rose-colour, while the seeds, which are of a bright orange, are enwrapped in a covering called an aril, by which they remain attached to the capsule after the valves have opened. Each capsule has five cells and five seeds, and each seed has a little white stalk attached to its aril, like the funicle of a pea. There are several species. The Celastrus is a climbing shrub, remarkable for its clusters of flowers, but which has nothing else to recommend it. The third section, Aquifoliaceæ, is made a separate order, under the name of Ilicineæ, or Aquifoliaceæ, by many botanists; some of whom place it in the sub-class Corollæfloræ, because the petals are connected at the base. The most common plants that it contains are included in the genera Ilex and Prinos. In _Ilex aquifolium_, the Holly, the corolla (_a_ in _fig._ 135), is in four or five petals connected at the base; there are four stamens, the cells of the anthers of which adhere to the sides of the filament (_b_). The berry (_c_) is four-celled, each cell containing a one-seeded nut. The leaves (_d_) are simple, and smooth, shining and prickly at the edges, which are curved upwards. Prinos, the Winter-berry, is a little evergreen shrub, with red berries. ORDER LX.—RHAMNACEÆ.