The Papilionaceous flower of the Pea, Bean, and nearly all
that family. In this we have an irregular corolla of a peculiar shape, which Linneus likened to a butterfly (whence the term, papilio being the Latin name for a butterfly); but the resemblance is not very obvious. The five petals of a papilionaceous corolla (Fig. 217) have received different names taken from widely different objects. The upper and larger petal (Fig. 218, s), which is generally wrapped round all the rest in the bud, is called the standard or banner. The two side petals (w) are called the wings. And the two anterior (k), the blades of which commonly stick together a little, and which enclose the stamens and pistil in the flower, from their forming a body shaped somewhat like the keel, or rather the prow of an ancient boat, are together named the keel.
FIG. 217. Front view of the papilionaceous corolloa of the Locust-tree. 218. The parts of the same, displayed. 1