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..
Perennial herbs, with flowering stems arising from the small rootstocks and alternate, entire or 3-7-lobed leaves. The flowers solitary or in terminal cymes, rarely represented by bulblets. Calyx-lobes 5, erect, usually with a terminal gland. Corolla white, regular, the petals somewhat narrowed at the base, but usually clawless. Stamens 10; filaments subulate. Ovary about one-half inferior, the carpels united to about the middle. Follicles well united, erect, except the more or less spreading tips, partly included in the calyx-tube. [Greek, stone-breaking, from reputed medicinal qualities.]
About 20 species, most abundant in the cooler parts of the northern hemisphere. Type species: Saxifraga granulata L.
Flowers below the terminal nodding flower replaced by bulblets; petals 4"-s" long.
Flowers not replaced by bulblets; petals about 2" long.
Saxifraga cernua L. Sp. Pl. 403. 1753.
Stem weak, slender, ascending, pubescent but scarcely glutinous, 4'-12' long. Leaves alternate, the basal, and lower ones petioled, broadly reniform, palmately 5-7-lobed, usually less than 1' wide; upper leaves smaller, sessile, 3-lobed or entire and bract-like, often bearing small bulblets in their axils; flowers 1-3, terminal, nodding, white, 8"-10" broad; petals obovate, sometimes retuse, 3-4 times as long as the ovate calyx-lobes.
Saxifraga rivularis L. Sp. Pl. 404. 1753.
Densely tufted, glabrous or sparingly pubescent, matted, •1'-3' high. Leaves alternate, the basal and lower ones slender-petioled, reniform, 3-5-lobed, seldom more than 3" wide; petioles dilated at the base; upper leaves lanceolate or ovate, entire or slightly lobed, mainly sessile; flowers 1-5, terminal, erect, white, about 3"-5" broad; calyx-lobes ovate, obtuse, slightly shorter than the ovate-oblong petals; tips of the capsule widely divergent, its base adnate to the calyx.
Alpine summits of the White Mountains, Labrador, arctic America and south in the Rocky Mountains to Colorado. Also in arctic and alpine Europe and Asia. Summer.