1. Hydroleaceae R. Brown
Hydrolea Family
Lawrence J. Davenport
Herbs or small shrubs, perennial, occasionally annual, semi-aquatic, erect or decumbent, unbranched or branched, to 6 dm, often gregarious, with new culms arising from prostrate stems. Stems succulent to woody, base often swollen; thorns 1 or 2 per node or absent. Leaves alternate, sessile or tapering to short (to 1 cm) petiole, estipulate. Inflorescences terminal corymbs, short-pedicellate, in clusters at branch tips, terminal leafy panicles, axillary fascicles (from compacted branchlets) on peduncles to 4 cm, or flowers solitary in leaf axils. Pedicels to 1 cm. Flowers: sepals persistent in fruit, 5, distinct, equal; petals 5, imbricate in bud, connate basally, equal; stamens 5, exserted or included, distinct, alternate with petals, inserted on short corolla tube, equal; anthers dorsifixed, 4-lobed, dehiscing longitudinally; disc absent; ovary superior; placentation axile, placentas adnate to thin septum, spongy, entire or 2-fid in cross section, bearing 100–200 anatropous ovules; styles persistent in fruit, 2–4, separate, equal. Fruits capsular, erect or drooping at maturity, dehiscence septicidal, loculicidal, or irregular. Seeds 100–200. x = 9, 10, or 12.
Genus 1, 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.
The genus Hydrolea has been segregated in its own family (R. Brown 1818) or included within the Hydrophyllaceae (A. Gray 1875; A. Brand 1913; L. J. Davenport 1988). Modern molecular data (M. W. Chase et al. 1993; M. E. Cosner et al. 1994; D. M. Ferguson 1998) and floral development studies (C. Erbar et al. 2005) support maintaining the Hydroleaceae as a distinct family.
SELECTED REFERENCES Davenport, L. J. 1988. A monograph of Hydrolea (Hydrophyllaceae). Rhodora 90: 169–208. Erbar, C., S. Porembski, and P. Leins. 2005. Contributions to the systematic position of Hydrolea (Hydroleaceae) based on floral development. Pl. Syst. Evol. 252: 71–83.
