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 slender more or less scaly rootstocks. Leaves basal, solitary or several together, with the petioles dilated at the base, palmately 3-foliolate; leaflets notched at the apex, usually with a membranous fold in the sinus. Scapes solitary or several together, topped by a single pedicel or rarely with an umbel-like cyme. Flowers perfect, homogonous. Sepals 5, the inner longer than the outer. Petals white or pink, delicate, much longer than the sepals, often obliquely notched at the apex. Stamens 10: filaments commonly glabrous. Capsule relatively short. Seeds few or several in each cavity, pitted and grooved or striate. [Greek, sour, from the acid juice.]
About 6 species, natives of the northern hemisphere, the following typical.
* Revised by Dr. J. K. Small.
Oxalis Acetosella L. Sp. Pl. 433. 1753.
Perennial by a scaly nearly unbranched root-stock, acaulescent, 2'-6' high, pubescent with scattered brownish hairs. Leaves 3-6, long-petioled; petioles jointed and dilated at the base; leaflets obcordate, wider than long; scapes 1-3, slightly longer than the leaves, I-flowered, 2-bracted above the middle; flowers broadly campanulate, about 4' long; sepals obtusish; petals white or pink, veined with deep pink, emarginate or entire, 3-4 times as long as the calyx; capsule subglobose, 1"-2" long, glabrous, its cavities 1-2-seeded; seeds ovoid, longitudinally grooved.
In cold damp woods, Nova Scotia to Saskatchewan, the mountains of North Carolina, and the north shore of Lake Superior. Cleistogene flowers are borne on recurved scapes at the base of the plant. Native also in Europe, Asia and northern Africa. Sleeping beauty. Ladies'- or sleeping clover. Sheep-sorrel. Cuckoo-flower. Old names, wood-sower or wood-sour, cuckoo's meat, sour trefoil, stub-wort, shamrock, hearts, sour-trifoly. Yields the druggists' " Salt of Lemons." May-July.