monosepalou

a. [ Mono- + sepal: cf. F. monosépale. ] (Bot.) Having only one sepal, or the calyx in one piece or composed of the sepals united into one piece; gamosepalous. [ 1913 Webster ]

☞ The most recent writers restrict this term to flowers having a solarity sepal, and use gamosepalous for a calyx formed by several sepals combined into one piece. Cf. Monopetalous. [ 1913 Webster ]