Papilionaceous flower

Flower parts of a Chinese wisteria. It has a diadelphous stamen morphology (one stamen not fused with the remaining nine), which Linnaeus classed as the Diadelphia.

Dissected flower parts of Sesbania bispinosa

Papilionaceous flowers (from Latin: papilion, a butterfly) are flowers with the characteristic irregular and butterfly-like corolla found in many, though not all, plants of the species-rich Faboideae subfamily of legumes. Tournefort suggested that the term Flores papilionacei originated with Valerius Cordus,^[1] who applied it to the flowers of the bean.^[2]