Elatine
Sp. Pl. 1: 367. 1753.
| Taxon | Illustrator ⠉ | |
|---|---|---|
 | Galphimia angustifolia Elatine rubella Elatine triandra | Karin Douthit Barbara Alongi Barbara Alongi |
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.
Distribution
North America, Mexico, South America, Europe, Asia, Africa, Pacific Islands, Australia
Discussion
Species ca. 25 (10 in the flora).
Selected References
Lower Taxa
Key
| 1 | Petals 2; capsules 2-locular. | Elatine minima |
| 1 | Petals usually 3–4, sometimes 0; capsules 3–4-locular. | > 2 |
| 2 | Sepals 4; petals 4; capsules 4-locular. | > 3 |
| 3 | Seeds curved 90–180°; pedicels 1.5–2.5(–3.5) mm, recurved in fruit; w United States. | Elatine californica |
| 3 | Seeds straight or curved to 15º; pedicels 0.1–23 mm, erect; Quebec. | Elatine ojibwayensis |
| 2 | Sepals 2–3 (rarely 4 in E. triandra); petals 3 (sometimes 0 in E. ambigua); capsules 3-locular. | > 4 |
| 4 | Pedicels recurved in fruit, 0.5–2.5 mm. | Elatine ambigua |
| 4 | Pedicels erect, 0–0.5 mm. | > 5 |
| 5 | Stamens 1–6, number variable within plant. | Elatine heterandra |
| 5 | Stamens 3. | > 6 |
| 6 | Seed pits ± round, (9–)14–17 per row. | Elatine brachysperma |
| 6 | Seed pits angular-hexagonal, (13–)16–35 per row. | > 7 |
| 7 | Seeds ellipsoid, pit length 3–5 times width; stipule margins entire. | Elatine chilensis |
| 7 | Seeds oblong or slenderly cylindric, pit length 1–3 times width; stipule margins dentate. | > 8 |
| 8 | Leaves reddish green; seed pit length 1–2 times width. | Elatine rubella |
| 8 | Leaves light green to green; seed pit length 2–3 times width. | > 9 |
| 9 | Leaf blades linear, lanceolate or narrowly oblong, apices acute or obtuse. | Elatine triandra |
| 9 | Leaf blades obovate or broadly spatulate, apices rounded to shallowly emarginate. | Elatine americana |