The flowers of the plants contained in this tribe have generally five regular, widely spreading petals, which are never joined together; and stamens of unequal length, which with few exceptions are also perfectly free. The petals are generally of the same size and shape; though sometimes, as in the Barbadoes Flower-fence (Poinciana, or Cæsalpinia pulcherrima), four are of the same shape, and one deformed (see fig. 18). The filaments of some of the stamens are very long and curving over, but the others are much shorter and erect; the style is long and slender, ending in a pointed stigma. The legume is flat, and it looks almost many-celled, from the seeds being divided from each other by a kind of spongy substance, frequently found in the pods of plants belonging to this division. The leaves are bi-pinnate, and the stem is spiny.
The Carob-tree, or St. John’s bread (Ceratonia siliqua), agrees with the Barbadoes Flower-fence in the pulpy matter dividing the seeds, though it differs widely in its flowers, which are without petals, and do not possess any beauty. The pulp of the pods of the Carob tree is eatable; but that of Poinciana is said to be injurious. The pod of the Tamarind (Tamarindus indica) differs from the preceding species in having the pulpy matter of its pods contained between the outer and inner skin of each valve, like the fleshy substance in the pod of the pea, instead of serving as a bed for the seeds. The flowers of the tamarind have five equal petals of a brownish yellow, three of them being streaked with pink; and the anthers are nearly rose-colour. The stamens and the style both curve upwards. It is the pods prepared with sugar that form what we call Tamarinds. In Cassia lanceolata, the leaves of which furnish senna, the flowers have a bright yellow corolla of five concave petals, three of which are somewhat larger than the others. The stamens are also unequal in length; and the style curves upwards. The legume is kidney-shaped, and the cells are divided from each other by thin membraneous partitions. The Gleditschia or Honey Locusts, now so frequently planted in our shrubberies on account of the lightness and elegance of their foliage, belong to this division, and some of them, particularly the Chinese Thorny Acacia (Gleditschia horrida), are remarkable for their thorns proceeding from the trunk and large branches, as well as from the axils of the leaves. The Logwood (Hæmatoxylon Campechianum), has inconspicuous yellow flowers, the petals being very little longer than the calyx; and the legume has seldom more than two seeds. Though it is considered a tree, the stem is seldom thicker than the arm of a man, and it is generally crooked; chips of the wood are used for dyeing purple. The Judas-tree (Cercis siliquastrum) is another species belonging to this division, as, though the flowers appear of the papilionaceous kind, they are, in fact, composed of five petals, nearly equal in size, but having the wings the largest. There are ten stamens, free, and of unequal length. The legume is oblong and many-seeded; and it opens only on the dorsal suture, the other side to which the seeds are attached being slightly winged. The flowers are each on a separate flower-stalk or pedicel, but they rise from the trunk and branches in tufts or fascicles. The leaves are simple and cordate; and they do not appear till the flowers have faded.
The Kentucky Coffee-tree (Gymnocladus canadensis) is the last plant belonging to this division that I shall attempt to describe. This tree is called in Canada, Chicot, or the stump-tree, from its having no visible buds, and thus appearing like a dead stump in winter. The flowers of this plant are white, and they are produced in racemes, but they bear no resemblance to the pea flowers, having rather a star-like appearance, like those of the Jasmine (see fig. 19).
Fig. 19.—Flowers of the Kentucky Coffee-tree. The calyx (a) is tubular; and the upper part or limb is divided into five parts (b), which alternate with the petals of the corolla (c). There are ten stamens, but they are completely enclosed in the tube of the calyx. The pod is very large, the valves becoming hard and bony when dry; and the seeds are like large beans, the pod being deeply indented between the seeds. The leaves are bi-pinnate, with from four to seven pairs of pinnæ; the lower having only one small leaflet, but the rest bearing from six to eight pairs of leaflets each. This tree must not be confounded with the true Coffee-tree, which belongs to Rubiaceæ, and from which it is perfectly distinct in every respect; and it only takes its American name from its beans having been used as a substitute for coffee. The outer bark of this tree, when it becomes old, splits off in narrow strips and rolls up; and its timber, like that of the Robinia or False Acacia, having very little sap wood, is thus very strong in quite young trees, though it is of little value when the tree is full-grown.
The species contained in the first and second divisions of this order will be easily recognised by botanical students; and though those of the third division are much more difficult to find out, still there is a kind of family likeness, particularly in the leaves, which will enable the eye, with a little practice, to recognise them. The student should visit the hothouses of botanic gardens and nurseries, and should there endeavour to pick out plants belonging to this order.