The World Flora Online

SELECTED REFERENCES

Hartog, C. den. 1970. The Sea-grasses of the World. Amsterdam. Haynes, R. R. and L. B. Holm-Nielsen. 1985. A generic treatment of Alismatidae in the Neotropics. Acta Amazon. 15(suppl.): 153--193. Phillips, R. C. and C. P. McRoy, eds. 1980. Handbook of Seagrass Biology: An Ecosystem Perspective. New York.

Herbs, perennial, rarely annual, rhizomatous, caulescent; turions absent. Leaves alternate, submersed, sessile; sheath persisting longer than blade or decaying with age into bundles of woolly fibers, not leaving circular scar when shed, not ligulate, auriculate with scarious lobes; blade linear; intravaginal squamules scales, more than 2. Inflorescences axillary or terminal, spadices, surrounded by spathe, pedunculate; peduncle following fertilization not elongating, not spiraling. Flowers unisexual, staminate and pistillate on same plant or different plants; subtending bracts (retinacula) often present; perianth absent. Staminate flowers: stamens 1; anthers dehiscing longitudinally; pollen linear. Pistillate flowers: pistils1, not stipitate; ovules pendulous, orthotropous. Fruits achenelike. Seeds 1; embryo straight.

Fls small and inconspicuous, hydrophilous, unisexual, arranged in 2 rows on one side of a flattened spadix subtended (and often largely enclosed by) a spathe, the axis of the spadix often with a series of ± well developed marginal lobes or appendages (retinacula) that fold over and ± cover the fls, the fls otherwise bractless and without perianth; stamen solitary; anther sessile, tetrasporangiate and dithecal; pollen filamentous, up to 2 mm, without exine; ovary solitary, bicarpellate, unilocular, with a single apical, pendulous ovule and 2 basally connate styles; fr small, drupaceous or firm and eventually opening irregularly; endosperm wanting; embryo with a basally closed and sheathing cotyledon lying in the groove of an enlarged hypocotyl; glabrous, rhizomatous, perennial marine herbs; lvs alternate, commonly distichous, parallel-veined or with only a midrib, generally ligulate at the juncture of the sheath and narrow blade. 3/15–20.

Herbs, perennial, rarely annual, in saline water, rhizomatous, caulescent. Leaves alternate, submersed, sessile, sheath persisting longer than blade or decaying into bundles of fibers, blade linear. Inflorescences axillary or terminal, spadices surrounded by spathe, pedunculate. Plants monoecious or dioecious; flowers unisexual; subtending bracts often present; perianth lacking. Male flowers with single stamen, anthers dehiscing longitudinally. Female flowers with single pistil. Fruit achenelike. Seed 1 with straight embryo.

Leaves distichous, linear or filiform; leaf sheath open or closed, often with stipuloid flanges, with an auriculate ligule at the junction with the blade; blade parallel-veined, sometimes with midrib Inflorescence of 1 to several spadices, each enclosed in a spathe formed by the sheath of the next leaf; flowers small, sessile in two rows on a flattened axis; pollination by water; petals absent, stamen 1, sessile, dorsifixed, anther with longitudinal slits, the pollen filamentous, without exine, with the same density as sea water; pistillate flower protogynous, gynoecium 1, 1- locular with basally united styles and two stigmatic arms; ovule single, pendulous, orthotropous, bitegmic Fruit a small irregular drupe, or irregularly dehiscing; endosperm absent Perennial herbs adapted to life in shallow sea water, with creeping rhizomes, monoecious or dioecious; rhizomes creeping or tuberous, nodes with intervaginal scales Inflorescence of 1 to several spadices, each enclosed in a spathe formed by the sheath of the next leaf; flowers small, sessile in two rows on a flattened axis; pollination by water; petals absent, stamen 1, sessile, dorsifixed, anther with longitudinal slits, the pollen filamentous, without exine, with the same density as sea water; pistillate flower protogynous, gynoecium 1, 1- locular with basally united styles and two stigmatic arms; ovule single, pendulous, orthotropous, bitegmic Fruit a small irregular drupe, or irregularly dehiscing; endosperm absent Perennial herbs adapted to life in shallow sea water, with creeping rhizomes, monoecious or dioecious; rhizomes creeping or tuberous, nodes with intervaginal scales