This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol1", 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..
Low fleshy glabrous perennial herbs, with erect stems. Leaves mostly basal, long-petioled, reniform or orbicular, cordate, palmately nerved, with cylindric ocreae. Flowers perfect, small, green, in terminal panicled racemes. Calyx unequally 4-parted, the outer segments smaller than the inner; stamens 6, included; filaments subulate. Ovary 1-celled; ovule solitary; style short, 2-parted, its branches divergent; stigmas fimbriate, persistent on the large wings of the fruit. Achene-body ovate, lenticular, broadly winged. Embryo straight, borne in the centre of the endosperm. [Greek, sour, from the acid leaves.]
Two known species, the following typical; one in the Himalayas.
Rootstock large, chaffy; stems scape-like, simple or sparingly branched, leafless or nearly so, 2'-12' tall. Leaves reniform or orbicular-reniform, 1/2'-1 1/2' wide, undulate, sometimes emarginate at the apex, the basal long-petioled; ocreae oblique, loose, those on the stem bearing flowers; racemes many-flowered; flowers slender-pedicelled; segments oblong, the inner erect, the outer reflexed in fruit; achene-body pointed, smooth, surrounded by a broad membranous wing.