There are three genera in this order: viz., Philadelphus, the Mock-Orange or Syringa; Decumaria and Deutzia, all which have white flowers. There are many species of Philadelphus, all of which are easily known by their large white flowers, and large coarse-looking leaves. The flowers of the common species (_P. coronarius_) smell like those of the Orange, and the leaves taste like cucumber. There is only one species of Decumaria (_D. barbara_), which is a native of Virginia and Carolina, and is a climbing shrub, with terminal corymbs of white, sweet-scented flowers. _Deutzia scabra_, though only introduced in 1833, is already common in gardens; and it is a general favourite from the great abundance of its flowers. Though it said to be not a true climber, its stems are too weak to stand without support. It is a native of Japan, and though generally kept in pots, it is supposed to be quite hardy. ORDER LXXXIV.—MYRTACEÆ.—THE MYRTLE TRIBE. No plants are more easily recognized than those belonging to this tribe; as they are easily distinguished by their entire leaves, which have no stipules, and which, when held up to the light, appear to be not only full of transparent dots, but to have a transparent line round the margin. The flowers have also abundance of stamens on long slender filaments which look like tufts of silk, and only four or five petals. The whole of the plants are fragrant, and every part of them seems full of an aromatic oil, which is particularly visible in the flower-buds of _Caryophyllus aromaticus_, which when dried form what are commonly called cloves; and in the leaves of some of the kinds of Eucalyptus. The genera may be divided into two sections, viz., those with a dry capsule for the fruit; in which are included _Melaleuca_ and its allied genera, _Eucalyptus, Callistemon, Metrosideros and Leptospermum_; and those with berry-like fruit, the most interesting of which are _Psidium_, the Guava; _Myrtus_, the Myrtle; _Caryophyllus_, the Clove; _Eugenia or Myrtus pimenta_, Jamaica Allspice; and _Jambosa Vulgaris or Eugenia Jambosa_, the Rose Apple. In some of the genera, as for example in Eucalyptus, the sepals of the calyx become detached at the base, and being united above form a sort of cap or calyptra, which is pushed off by the stamens when the flower begins to expand. Besides the plants already enumerated, some botanists add another section to Myrtaceæ, which others consider a separate order; under the name of _Lecythideæ_. This section contains three genera, the most remarkable plants in which are the Cannon Ball-tree (_Lecythis Ollaria_), and the Brazil Nut (_Bertholletia excelsa_). The fruit of this last plant is fleshy, and as large as a child’s head, opening with a lid, and containing sixteen or twenty triangular seeds, laid over each other in a regular manner, which are the Brazil-nuts sold in the shops. ORDER LXXXV.—CUCURBITACEÆ.—THE GOURD TRIBE.