Herbs, perennial or annual. Roots thin or tuberous. Leaves 2-ranked or spirally arranged, not glaucous; blade sessile or petiolate. Inflorescences terminal, leaf-opposed; cymes 1--2, enclosed in spathes, proximal cyme several-flowered, distal cyme vestigial or with 1--several staminate flowers; spathes often filled with mucilaginous liquid, margins distinct or basally connate; bracteoles usually absent. Flowers bisexual and staminate, bilaterally symmetric; pedicels well developed; sepals distinct or proximal 2 connate, unequal; petals distinct, proximal petal often different color than distal 2, smaller or subequal, distal 2 blue (occasionally lilac, lavender, yellow, peach, apricot, or white), clawed; stamens (5--)6, proximal 3 fertile, medial different in form, size from others, distal (2--)3 staminodial; filaments glabrous; antherodes commonly 4--6-lobed; ovary 2--3-locular, ovules 1--2 per locule, 1-seriate. Capsules 2--3-valved, 2--3-locular. Seeds 1--2 per locule; hilum linear; embryotega lateral. x = 11--15.

PLANT: Annual or perennial herbs, the roots thin or tuberous. STEMS prostrate to erect. LEAVES lanceolate to linear lanceolate. STEMS: prostrate to erect. LEAVES: lanceolate to linear lanceolate. INFLORESCENCE: terminal and leaf-opposed, composed of 1-2 cymes enclosed in spathes, the upper cyme lacking or producing 1 staminate flower, the lower cyme several flowered; spathes with margins free or fused basally, often filled with mucilaginous liquid. FLOWERS: perfect or staminate, zygomorphic; sepals free or lower 2 connate; petals free, the upper 2 usually blue (occasionally lilac or lavender), clawed, the lower petal often smaller and different in color from the upper 2; stamens 6, the upper 3 staminodial, the sterile anthers commonly 4-6 lobed, the lower 3 stamens fertile, the medial different in form and size from the others; ovules 1-2 per locule. FRUITS: 2-valved, 3-locular on ours. SEEDS: 1-5, testa rugose or smooth, tan to brown, hilum linear. NOTES: Ca. 170 species: almost cosmopolitan, mainly tropical (for Jan and Kaspar Commelijn). REFERENCES: Puente, Raul, and Robert B. Faden. 2001. Commelinaceae. J. Ariz. – Nev. Acad. Sci. Volume 33(1).