Herbs, annual. Roots thin. Leaves spirally arranged; blade occasionally sessile [usually petiolate], glaucous. Inflorescences terminal or terminal and axillary, 1[–several] elongate cyme[s], [occasionally axillary and perforating sheaths], subtended by spathaceous bract; bract leaflike; bracteoles persistent. Flowers bisexual [bisexual and staminate], bilaterally symmetric; pedicels well developed; sepals distinct, subequal; petals distinct, unequal, not clawed, proximal petal small [large], distal 2 blue or blue-violet [white to pink], equal, large; stamens 6, all fertile, polymorphic; proximal 3 stamens long, lateral filaments bearded; medial glabrous, anthers large; distal 3 stamens short, filaments densely bearded, anthers small; filaments connate basally; ovary 3-locular; ovules 2–several per locule, 1-seriate. Capsules 3-valved, 3-locular. Seeds 2–several per locule; hilum linear; embryotega lateral. x = 13, 14, 16, 17.
Tex., tropical America, especially Mexico to Nicaragua.
The reproductive features of B. C. Tharp’s two species of Commelinantia (1922) clearly link them with Tinantia (O. Rohweder 1962). My research indicates that although some attributes, including pollen and chromosome number, can still be used to separate Commelinantia from Tinantia, these characters are not of sufficient import to merit separate generic status.
Species ca. 14 (1 in the flora).