This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Herbs with creeping, ascending or floating stems, the leaves petioled, with cordate, ovate, oval or reniform blades, or grass-like. Spathes 1-flowered or several-flowered. Flowers small, white, blue or yellow. Lobes of the perianth nearly or quite equal, linear. Stamens 3, equal or unequal, inserted on the throat of the perianth. Ovary fusiform, entirely or incompletely 3-celled by the intrusion of the placentae; ovules numerous; stigma 3-lobed. Fruit an ovoid many-seeded capsule, enclosed in the withered perianth-tube. Seeds ovoid, many-ribbed. [Greek, referring to the unequal anthers of some species.]
Leaves reniform, oval or ovate.
One of the filaments longer than the other two; flowers few or several.
Flowers white, little exserted from the sheath; leaves reniform.
Flowers blue, much exserted; leaves ovate to subreniform.
Filaments broad, equal; spathe 1-flowered; leaves ovate to oval.
Leaves linear, grass-like, floating.
Stems creeping in the mud, rooting at the nodes. Leaves long-petioled, the blades reniform, wider than long, 8"-2o" wide, rounded at the apex; petioles sheathing, 1'-4' long; spathe few-flowered; inflorescence little exserted; tube of the perianth straight or slightly curved, slender, about 4" long, its lobes shorter; flowers white or pale blue; anthers basifixed, the 2 upper oval, the other on a longer filament and linear; fruit oblong.
Heteranthera peduncularis Benth. PI. Hartw. 25. 1840.
Stem stout, creeping on the mud or floating, rooting at the nodes, much branched, often 1° long or longer. Leaves long-petioled, the blades ovate to subreniform, 2 1/2' long or less, acute, obtuse or cuspidate at the apex, cordate at the base; spathe several-flowered, the inflorescence much exserted; flowers blue; perianth-tube nearly 5" long, straight or nearly so, the lobes much shorter than the tube; filaments slender, one of them longer than the other two; anthers basifixed, sagittate; fruit narrowly oblong, about 5" long.
Ponds, Nebraska(?), Missouri and Kansas to Mexico. July-Sept.
Pontederia limosa Sw. Prodr. 57. 1788.
Heteranthera limosa Willd. Neue Schrift. Ges. Nat. Fr.
Berlin 3: 439. 1801. Leptanthus ovalis Michx. Fl. Bor. Am. 1: 25. 1803.
Stems commonly much branched from the base, 6'-15' long. Leaves numerous, oval or ovate, obtuse at the apex, rounded or slightly cordate at the base, 1' long or less; petioles 2'-5' long; spathes i-flowered, often on peduncles 1' long or more; flowers- white or blue, usually larger than those of the preceding species; filaments broad, equal or nearly so; anthers linear, often sagittate.
In mud or shallow water, Virginia to Kentucky, Missouri, Nebraska, Florida, Louisiana and throughout tropical America. July-Sept.
Commclina dubia Jacq. Obs. Bot. 3: 9. pi. 50. 1768. Leptanthus gramineus Michx. Fl. Bor. Am. 1: 25. 1803. Heteranthera graminea Vahl. Enum. 2: 45. 1806. Schollera graminea A. Gray, Man. 511. 1848. Heteranthera dubia MacM. Met. Minn. 138. 1892.
Aquatic, stem slender, forked, often rooting at the nodes, 2°-3° long. Leaves linear, flat, elongated, acut-ish, finely parallel-nerved, their sheaths thin, furnished at the top with small acute stipule-like appendages; flowers light yellow, the perianth-segments narrow; stamens nearly equal; tube of the perianth very slender, 1'-1 1/2' long; spathe 1-2-flowered; filaments dilated below; anthers linear, 2" long, sagittate; style shorter than the stamens; stigma several-lobed; capsule 1-celled with 3 parietal placentae, many-seeded.
In still water, Quebec to Oregon, south to Florida and Mexico. Also in Cuba. Occasionally occurs in a small form on muddy shores. July-Oct.