[+] Flowers perfect, spiked or clustered; anthers 4 or 2, sessile; leaves alternate.
3. Potamogeton. Spike peduncled. Sepals 4, herbaceous. Anthers 4. Ovaries 4, sessile.
4. Ruppia. Flowers on an enclosed spadix, at length long-exserted, without perianth. Anther-cells 4, distinct. Ovaries 4, becoming stipitate.
[+][+] Flowers monœcious or diœcious, axillary, naked, monandrous; leaves opposite (alternate in n. 6).
5. Zannichellia. Monœcious. Pistils (2–5) from a cup-shaped involucre or sheath.
6. Zostera. Pistils and stamens alternate in 2 vertical rows on the inner side of a leaf-like enclosed spadix. Stigmas 2, linear. Stem creeping.
7. Naias. Diœcious; pistil solitary, naked. Stamen enclosed in a membranous spathe. Stems floating, with opposite or ternate leaves.
1. TRIGLÒCHIN, L. Arrow-grass.
Sepals and petals nearly alike (greenish), ovate, concave, deciduous. Stamens 3–6; anthers oval, on very short filaments. Pistils united into a 3–6-celled compound ovary; stigmas sessile; ovules solitary. Capsule splitting when ripe into 3–6 carpels, which separate from a persistent central axis.—Perennials, with rush-like, fleshy leaves, below sheathing the base of the wand-like naked and jointless scape. Flowers small, in a spiked raceme, bractless. (Name composed of τρεῖς, three, and γλωχίν, point, from the three points of the ripe fruit in n. 1 when dehiscent.)
[*] Fruit of 3 carpels.