Papilionaceous

Papilionaceous, or Butterfly-like (from the Latin papiliu. "a butterfly"), is the term applied to the corolla characteristic of a large sub-order of the order Leguminosai (q.v.), including all our British species of peas, vetches, clovers, etc. Such a corolla consists of five petals, the odd posterior one, known as the standard or vexillum, being generally relatively large, erect, and exterior. It overlaps two lateral petals, the wings or alee, and they in turn overlap the two anterior and generally horizontal heel-petals or carina; which are often confluent towards their apices. The petals have claws, are curiously interlocked or modelled over one another, and often differ in colour.