What does "monopetalous" mean?

Monopetalous: Having only one petal, or the corolla in one piece, or composed of petals cohering so as to form a tube or bowl; gamopetalous. Note: The most recent authors restrict this form to flowers having a solitary petal, as in species of Amorpha, and use gamopetalous for a corolla of several petals combined into one piece. See Illust. of Gamopetalous.