UW Burke Herbarium species comparison

Leaves mostly emersed, but often submerged and the blades floating;

blades sagittate or hastate, up to 2.5 dm. long and nearly as broad; submerged leaves sometimes bladeless and greatly elongate, 4-10 mm. broad.

Submersed or emersed, margins entire;

leaves under water phyllodial, sessile, flattened above and beneath, up to 26 cm long and 0.5 cm broad;

leaves above water petiolate, petioles somewhat triangular and 21-70.5 cm long, blade linear-ovate to ovate, 4.6-16.4 cm long and 0.7-6.1 cm broad.

Flowers in 2-8 whorles of 3 in bracteate racemes, the bracts 5-10 mm. long, blunt, hooded; pedicles 1-5 cm. long, ascending, in both the pistillate flowers (lower whorles) and staminate flowers.(upper whorles), or the plants sometimes monoecious;

sepals 3, 5-10 mm. long, persistent;

petals 3, white, twice as long as the sepals;

stamens more than 20;

pistils many on a globose receptacle.

Inflorescences bracteate racemes with 3-9 whorls, above water, 2.5-10 cm long and 2-4.5 cm broad;

peduncles 22-60 cm long;

bracts connate greater than ¼ total length, lanceolate, 2-5.5 mm, delicate, not papillose; fruiting pedicels spreading to bending backwards, cylindric to 0.5-3 cm;

flowers imperfect, to 1.8 cm in diameter;

sepals 3, curving backward to spreading, not encasing the flower or fruiting head, persistent;

petals 3, white, deciduous;

filaments widened, longer than anthers, pubescent;

anthers 2-chambered, splitting longitudinally; pistillate flowers pedicellate, sterile stamens absent.

Achenes 2.5-4 mm. long, winged, with a stylar beak strongly up-turned, 0.5-1.5 mm. long.

Fruiting heads 0.7-1.2 cm in diameter;

achenes oblanceoloid with no abaxial keel, 1.2-2 mm long and 0.8-1.2 mm broad, beaked;

faces tuberculate, wings 0, glands 0;

beak lateral, horizontal to erect, 0.3-0.6 mm.