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..
Arenaria serpyllifolia L. Sp. Pl. 423. 1753.
Annual, slender, slightly downy-pubescent, widely branched and diffuse, 2'-8' high. Leaves ovate, 2"-4" long, 1 1/2"-2" wide, acute; pedicels slender, 2"-6" long; bracts ovate, resembling the leaves; flowers 2" broad or less, very numerous in cymose panicles; sepals ovate, 1 1/2" long, acute or mucronate, 3-5-nerved, scarious-margined; petals obovate or oblong, usually shorter; capsule ovoid, slightly shorter than or equalling the calyx, dehiscent by 6 short apical valves; seeds rough.
Arenaria leptoclados Reichenb.; Guss. Fl. Sic. Syn. 2: 284. 1844.
Annual, tufted, much branched, roughish-puberulent, resembling Arenaria serpyllifolia L. Leaves lanceolate or ovate-lanceolate, 1 1/2"-2 1/2" long, about one-half as wide as long, acute or acuminate; bracts similar to the leaves, but usually much smaller; sepals lanceolate, acuminate, narrowly scarious-margined; petals oblong, about half as long as the sepals; capsule oblong or subcylindric, equalling the calyx or a little longer.
Dry soil, Maine to Michigan and westward. Ad-ventive from Europe. May-July.
Arenaria ciliata L. Sp. Pl. 425. 1753.
Perennial, tufted, glandular-puberulent, stems very slender, creeping or ascending, pubescent in lines, 1'-5' long, or the flowering branches erect. Leaves ovate or oblong, obtuse or acute at the apex, sessile or very nearly so, 1"-3" long, ciliate or glabrous; peduncles filiform, erect, mostly I-flowered; flowers about 3" broad; sepals ovate or oblong, obtuse, nerveless or faintly I-nerved, about as long as the petals; capsule oblong, twice as long as the calyx, its 3 valves deeply 2-cleft; seeds slightly roughened.
Quebec to Greenland. Also in arctic and alpine Europe. The American plant is referred by Dr. B. L. Robinson to the var. humifusa Hornem. - having glabrous leaves and nerveless sepals so far as observed, and may be specifically distinct from the European. In Europe the species has been separated into several varieties. Summer.
Arenaria Hookeri Nutt.; T. & G. Fl. N. A. 1: 178. 1838.
Tufted from a deep woody root, 2-3' high. Leaves linear-subulate, rigid, very sharp-pointed, densely impricated, glabrous, 6"-12" long; flowering stems short, finely and densely pubescent; bracts lanceolate-subulate, scarious-margined, the margins ciliolate; cyme dense, 8"-18" broad, its rays short and pubescent; sepals lanceolate-subulate, pubescent, shorter than the similar bracts and about one-half the length of the petals; capsule not seen.
In dry or rocky soil, South Dakota, Nebraska and Colorado to Wyoming and Montana. June-Aug.