Flora of North America species comparison

1–3 mm diam.

rhizomatous, creeping, with abbreviated erect axis at nodes, or erect, leafy, elongate.

whorled, recurved, 10–40 × 1.5–4.5 mm.

basal, alternate, opposite, or whorled, sessile or petiolate;

stipules sometimes present, forming tubular sheath around stem;

blade margins entire or serrate;

veins 1–many.

axillary, terminal, or scapose, 1-flowered or cymose, subtended by spathe;

spathe a 2-fid bract or pair of opposite bracts.

unisexual, staminate and pistillate on same plants or on different plants, often with rudiments of opposite type, or bisexual, actinomorphic, rarely slightly zygomorphic;

perianth epigynous, free, mostly 6-parted, then differentiated into sepals and petals, rarely 3-parted, then petals absent in Thalassia and Halophila;

stamens (0–)2–many in 1 or more whorls (inner often staminodial), epigynous, distinct or ± connate;

pollen spheric, in monads or tetrads or in slender chains;

ovary 0–1, if present, inferior, 2–6[–16]-carpellate, 1-locular or falsely 6–9-locular;

placentation parietal.

berrylike.

many, fusiform, ellipsoid, ovoid, or spheric;

seed coat glabrous, papillose, or echinate.

spathes 2–4-flowered, 7.5–12 mm;

pedicel to 80 mm.

= 46.