Protologue Description: Anemone riparia. Plant comparatively slender, 3 to 9 dm. high, glabrate or loosely pubescent especially on the petioles and at the base of the involucre: leaves thin, 3-divided, the cuneate-lanceolate or cuneate-ovate divisions unequally cleft into coarsely and sharply toothed segments, the lateral divisions very deeply cleft: involucre 3-leaved, subtending the 1 to 5 slender elongated naked or invollucellate sometimes proliferous appressed-silky peduncles.: sepals unequal, oval or obovate, obtuse or acutish, 1.5-2 cm. long, thin, clear-white, canescent-tomentose or glabrate without: heads of carpels oblong, short cylindrical, 1.5-2 cm. long , scarcely 1 cm. thick; the slender persistant styles ascending or appressed much as in A. cylindrica.- A. cylindrica, var. alba, Oakes, Hovey's Mag. vii. 182. A. virginiana, var. alba, Wood, Class Book, 203.- Abundant on rocky banks and in the crevices of wet calacreous-slate ledges along the Piscataquis River, Dover, Maine, collected by the author June 25, 1894, August 31, 1897 and June 11, 1898, no. 2201; also collected at Dover by Geo. B. Fernald, June, 1896.