General: Aquatic or semi-aquatic perennial rooting in mud; stems leafy, 2-40 cm long, with or without small membranous ridges between the leaf-bases.
Leaves: All opposite; submerged leaves linear, single-veined, notched at the tip, 5-25 mm long; floating and emergent leaves broadly egg-shaped or oblanceolate, 3-veined, up to 1 cm wide.
Flowers: Inflorescence of tiny, inconspicuous flowers borne with a pair of tiny bracts, stalkless or shortly-stalked; styles 1-5 mm long, ascending.
Fruits: Achene-like, 4, each 1-seeded, wingless or scarcely wing-margined, rounded, egg-shaped or heart-shaped, irregularly pitted.
Notes: Two subspecies occur in our region.
1. Fruits egg-shaped or slightly heart-shaped in outline, broadest above the middle; submersed leaves usually wider than the stem; plants long-stemmed........................ ssp. bolanderi (Hegelm.) Calder & Tayl.
1. Fruits usually more nearly round or egg-shaped in outline; submersed leaves much narrower than the flattened stem; plants short-stemmed....................... ssp. heterophylla
Shallow ponds, slow-moving streams and shorelines in the lowland and montane zones; ssp. bolanderi- frequent on S Vancouver Island, rare in SE BC, ssp. heterophylla - rare in coastal BC; N to AK, YT, NT, E to NF and S to GA, TX, OK and CA; South America (ssp. bolanderi).
