any member of the genus Commelina (family Commelinaceae), which includes about 100 species of weak-stemmed herbs of wide distribution, only a few of ... Found on http://www.britannica.com/eb/a-z/d/15
Day'flow`er (-flou`ẽr) noun (Botany) A genus consisting mostly of tropical perennial herbs ( Commelina ), having ephemeral flowers. Found on http://www.encyclo.co.uk/webster/D/9