_Adiantum fronde supra-decomposita bipartita_, _foliis partialibus alternis_, _foliolis trapeziformibus obtusis_, Gronovius, Flora Virginica (1739), p. 123. (For other ancient references see Linnæus, as quoted above.) _Adiantum boreale_, Presl, Tent. Pterid., p. 158. Hab.—In rich, moist woods, especially among rocks. Common from New Brunswick and Canada southward to Central Alabama, Professor Eugene A. Smith, and westward to Lake Superior, Wisconsin, and Arkansas. Also in Utah, California, Oregon, British Columbia, the islands of Alaska, Kamtschatka, Japan, Mantchooria, and the Himalayan provinces of India. Ruprecht speaks of specimens from Newfoundland, and Professor Gray informs me that it exists in De La Pylaie’s collection from that island. Description.—The root-stock is elongated and creeping. It is about the diameter of a goose-quill, is covered with minute ovate scales, roots copiously from beneath and along the sides, and produces fronds from the right and left sides alternately. The stalks are usually from a foot to fifteen inches high, and from half a line to a line in thickness. When very young, they bear a few scattered narrow scales; but these soon fall off, leaving minute pointed scars. The mature stalk is roundish in section, the convexity being greatest on the side which corresponds to the under surface of the frond. The two convexities, anterior and posterior, are separated by two obscure angles or ridges, which extend the whole length of the stalk. The anterior, or flatter, convex surface is nearly black, while the other side is a dark purplish brown. The fibro-vascular bundle is U-shaped near the base of the stalk; but higher up it is more like a broad, open V; and just below the forking of the stalk it separates into two portions. The two branches of the stalk diverge at an angle of about fifty degrees, and rise obliquely, gracefully recurving till they nearly meet again. From the outer side of the curve each branch sends out from two to seven slender diverging branchlets, which are the rachises of the pinnæ. The branchlets nearest the forking of the stalk are from four to fifteen inches long, those more remote successively shorter. Thus the whole frond is from five or six to fifteen or eighteen inches broad, and, while somewhat funnel-form in the centre, radiates nearly horizontally towards the circumference. A pressed specimen can give but little idea of its graceful position.