This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol2", 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..
Characters of the family. The affinities are variously regarded by botanical authors, some placing it in Haloragidaceae, some in Onagraceae, others near Euphorbiaceae, the position here maintained. [Greek, beautiful hair, from the hair-like stems.]
About 20 species, of very wide geographic distribution. Besides the following, about 7 others occur in the southern and western parts of North America. Type species: Callitriche palustris L.
Fruit short-peduncled; bracts wanting; terrestrial.
Fruit sessile; aquatic, or some forms growing in mud.
Fruit oval, flat on the face, longer than the styles.
Fruit obovate, plano-convex, shorter than the styles.
Bracts none; leaves all linear, submersed.
Callitriche terrestre Raf. Med. Rep. (II.) 5: 358. 1808? Callitriche deflexa var. Austini Hegelm. Ver. Bot. Ver. Brand.
Tufted, the branches spreading on the ground or ascending, ą-2' long. Leaves spatulate or obovate, 3-nerved, 1 1/2"-2" long, about 1" wide, obtuse, tapering at the base into a short margined petiole, destitute of stellate scales; fruit about i" long and nearly 1/2" broad, deeply notched at both ends, its lobes with a narrow marginal wing or raised border, with a deep groove between them; peduncle shorter than or slightly exceeding the fruit; styles persistent, not longer than the fruit, spreading or reflexed.
* Text written for the first edition by the late Rev. Thomas Morong, here slightly revised.
Callitriche palustris L. Sp. Pl. 969. 1753.
Callitriche verna L. Fl. Suec. Ed. 2, 4. 1755.
Callitriche vernalis Koch, Syn. Fl. Germ. Ed. 2, 245. 1837.
Aquatic or growing in the mud, stems 2'-10' long. Submerged leaves linear, I-nerved, retuse or bifid at the apex, 5"-10" long; emersed or floating leaves obovate, obtuse, truncate or retuse at the apex, narrowed at the base into a margined petiole, dotted with stellate scales; aquatic forms occur with the leaves all linear; fruit 2-bracted, oval, 1/2"-1" long, about one-half as broad, nearly flat on the face, slightly notched at the apex, winged only toward the apex, or all around, separated by a deep groove.
Callitriche heterophylla Pursh, Fl. Am. Sept. 3. 1814.
Similar to the preceding species, either aquatic or growing in the mud. Fruit smaller, mostly obovate, usually slightly less than 1/2" long, and about the same breadth, broadly notched at the apex, thick, plano-convex, almost ventricose at the base; lobes obtusely angled with a small intervening groove, wingless, or with a narrow wing or raised border on the margins; styles usually longer than the fruit, erect.
In ponds and slow streams, Newfoundland to Manitoba, Florida, Missouri, Colorado and Louisiana. July-Sept.
Entirely submerged. Leaves crowded, linear or linear-lanceolate, clasping at the base, retuse or bifid at the apex, I-nerved, 5"-8" long, without stellate scales; fruit sessile, or rarely minutely pedunculate, orbicular or slightly narrower than long, 1/2"-1" in diameter, its lobes separated by a deep groove and broadly winged on the margins; styles as long as the fruit, or shorter, soon deciduous; bracts none.
In flowing water, Quebec and Lake Champlain to Michigan, Manitoba and Oregon, south in the Rocky Mountains to Colorado. Also in Europe and Asia. July-Sept.