Herbs annual, aquatic. Stem prostrate, slender, rooting at nodes. Leaves opposite or verticillate, shortly petiolate; leaf blade small, margin usually entire. Flowers usually only 1 per node, very small. Sepals 2-4, united at base, membranous, apex subacute. Petals 2-4, longer than sepals, apex obtuse. Stamens 1 or 2 × as many as petals. Ovary globose, compressed, 2-4-loculed, apex truncate; ovules numerous; styles 2-4; stigmas capitate. Capsule membranous, 2-4-septicidal. Seeds straight, curved, or horseshoe-shaped, surface reticulate-striate with hexagonal or elliptic pits.
Herbs, submersed or emergent aquatic, glabrous. Stems erect, ascending, decumbent, or prostrate, with longitudinal air spaces, rooting at nodes. Leaves: stipules membranous; petiole present or absent; blade margins entire, with hydathodes. Inflorescences: flowers usually solitary, sometimes 2[–3] per node. Pedicels present or absent. Flowers: sepals 2–4, connate basally, equal or 1 smaller, not carinate, apex obtuse; petals (0 or) 2–4, apex obtuse; stamens [0–]1–8; pistil 2–4-carpellate, ovary 2–4-locular, apex truncate; styles 2–4; stigmas 2–4. Capsules membranous. Seeds 2–33[–44] per locule, brown to yellowish brown, straight or curved (nearly circular in E. californica), surface with hexagonal, rectangular, elliptic, or ± round pits (pits oriented with longer dimension at right angles to length of seed). x = 9.
"Sep and pet each 2–4; stamens as many (in our spp.) or twice as many as the sep; ovary 2–4-locular, the placentas axile or basal-axile; seeds several per cell, cylindric, minutely areolate; small aquatic annuals with inconspicuous axillary fls and thin- walled frs. 20, widespread."
Leaves opposite or more rarely verticillate; stipules present.
Small glabrous herbs, aquatic or found in damp situations.
Fruit globose; somewhat depressed at the apex, wall membranous; seeds numerous, straight or curved; testa with a scalariform reticulation.
Ovary globose, 3–4-locular; styles minute, 3–4, spreading.
Stamens as many as the petals or twice the number.
Sepals 2–4 shortly connate at the base, obtuse.
SELECTED REFERENCES Duncan, W. H. 1964. New Elatine populations in the southeastern United States. Rhodora 66: 47–53. Fassett, N. C. 1939. Notes from the herbarium of the University of Wisconsin. No. 17. Elatine and other aquatics. Rhodora 41: 367–377. Fernald, M. L. 1917. The genus Elatine in eastern North America. Rhodora 19: 10–15. Fernald, M. L. 1941b. Elatine americana and E. triandra. Rhodora 43: 208–211.
|Waterwort, élatine [Greek name for a plant with firlike leaves]|
Gordon C. Tucker
Donald H. Les "Elatine Linn. in Flora of North America @ efloras.org" eFlora. Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA., 2017. Web. Accessed February 2018.