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..
Cerastium aquaticum L. Sp. Pl. 430. 1753.
Stellaria aquatica Scop. Fl. Carn. Ed. 2, 1: 319. 1772.
Perennial, stem angled, mostly glandular-pubescent above, nearly glabrous below, ascending or decumbent, branched, 1°-2 1/2° long. Leaves ovate or ovate-lanceolate, acute at the apex, the upper sessile and subcordate, the lower petioled, rounded at the base, 1'-2' long; flowers about 1/2' broad, solitary in the forks of the stem and in terminal cymes; pedicels slender, glandular, deflexed and much longer than the calyx in fruit; calyx campanulate; sepals ovate, acute, about one-half as long as the 2-cleft petals; stamens 10; styles 5, alternate with the sepals, rarely 6; capsule ovoid-oblong, slightly longer than the calyx; seeds rough.
Stellaria humifusa Rottb. Skrift. Vid. Selsk. 10: 447. 1770.
Alsine humifusa Britton, Mem. Torr. Club 5: 150. 1894.
Glabrous, stems branching, spreading and ascending, 1' - 3' long, purplish. Leaves ovate or oblong, fleshy, 2"-3" long, acutish or obtuse, sessile; bracts foliaceous; flowers few or solitary, terminal or axillary, 3"-5" broad; sepals ovate-lanceolate, acute or acutish, 2" long; petals 2-parted, equalling or somewhat exceeding the calyx; capsule ovoid, as long as the sepals; seeds smooth, brown.
Stellaria uliginosa Murr. Prodr. Goett. 55. 1770. Alsine uliginosa Britton. Mem. Torr. Club 5: 150. 1894.
Weak, decumbent or ascending, slender, generally growing in dense masses, stems nearly simple, 6'-16' long. Leaves oblong to oblong-lanceolate, 5"-12" long, 2"-5" wide, narrowed at the base, the lower slightly petioled and sometimes ciliate, the upper sessile; flowers 3" broad, in lateral sessile cymes, rarely terminal; pedicels slender; sepals 1"-1 1/2" long, lanceolate, acute; petals 2-parted, about the length of the calyx and the ovoid pod; seeds rough.
In cold brooks and springs, Maryland, eastern Pennsylvania and western New Jersey, north to Newfoundland, and in Michigan. Also in British Columbia and the Northwest Territory, Europe and Asia. Bog-, swamp- or marsh stitchwort. Summer.