1. Hydrolea Linnaeus, Sp. Pl. Ed. 2,. 1: 328. 1762; Gen. Pl. ed. 6, 124. 1764. name conserved.
[Greek hydor, water, and elaia, olive, probably alluding to habitat and oiliness and/or form of leaves]
Herbs or small shrubs, usually perennial. Stems green, brown, or purple, glabrous or hispid-hirsute, with or without glandular trichomes or long, jointed hairs; thorns occasionally bearing small leaves toward tips. Leaf blades ovate, lanceolate, or linear, occasionally orbiculate, pinnately veined, base attenuate, acute, round, or obtuse, margins entire or serrulate, often undulate, apex acuminate to acute, surfaces glabrous or densely pubescent, sometimes gland-dotted, with or without glandular trichomes or long, jointed hairs, occasionally pubescent only along main veins. Inflorescences terminal or axillary, pedunculate, highly branched or unbranched. Flowers: sepals lanceolate or ovate, margins entire, surfaces glabrous or hispid-hirsute, with or without glandular trichomes or long, jointed hairs; corolla blue or white, campanulate; anthers pale pink, white, or blue; filaments white or blue, abruptly dilated at base, glabrous; pollen white or yellow; ovary green or blue, globose or subglobose, proximal 1/2 glabrous, distal 1/2 glabrous, puberulent, or glandular-pubescent; styles white, brown, or blue, often curved inward to summits, glabrous, puberulent, or glandular-pubescent (especially at base); stigmas funnelform. Capsules brown or purple, globose or ovoid, occasionally truncated at style bases, 3–7 × 2.5–7 mm, proximal 1/2 glabrous, distal 1/2 glabrous, puberulent, or glandular-pubescent. Seeds tan to dark brown, ovoid to cylindric, symmetric or occasionally asymmetric, 0.4–0.7 × 0.2–0.4 mm.
Species 11 (5 in the flora): sc, e United States, Mexico, Central America, South America, s, se Asia, Africa, Indian Ocean Islands (Madagascar), Pacific Islands (Philippines), n Australia.
Species in the flora area are placed in Hydrolea sect. Hydrolea.
