Description.—The root-stock is rather stout, ascending or erect; and its apparent thickness is much increased by the persistent bases of stalks, which also give it a dense covering of broad bright-brown chaffy scales. The fronds, frequently to the number of six or eight, besides old and shrivelled ones, stand in a crown at the upper end of the root-stocks, resting on stalks from one to four inches long, which are usually very chaffy, the chaff continued along the rachis and midribs, though composed of smaller scales than those lower down. The fronds are from three or four to ten inches in length; and the greatest breadth, just above the middle, is from one-fifth to one-sixth of the length. The outline is exactly lanceolate, as the apex is acute, and the lower part gradually tapering to a somewhat narrowed base. The fronds are delicately, but densely, bipinnate. In a frond nine inches long there are about thirty primary pinnæ on each side, and in one of the middle pinnæ about ten oblong-ovate obtuse pinnately-incised pinnules on each side. The pinnules are from a line to two lines long, and are adnate to the secondary rachis by a more or less decurrent base. In large fronds the teeth of the pinnules are again crenately toothed; but in small specimens the pinnules themselves are entire, or but slightly toothed. Two sterile fronds collected by Professor M. W. Harrington, in Iliuliuk, Alaska, are broadly ovate-lanceolate in outline, and have acute primary pinnæ; and other specimens, some from Eastern Canada, collected by Mr. Watt, and some from Northern Wisconsin, collected by Mr. Lapham, are much slenderer and less scaly than usual. This is the var. β of Hooker. Usually the fronds are rather rigid, full-green above, a little paler beneath, and both surfaces, together with the rachis, especially the canal along the upper side of the rachis, are dotted with very minute pellucid pale amber-colored glands. The fronds commonly fruit very fully, even the lowest pinna bearing sporangia. The indusia are very large, thin, orbicular, with a narrow sinus, more or less ragged or toothed and gland-bearing at the margin, and are so dense as to overlap each other, and nearly conceal the back of the pinnules. The spores are ovoid, and have a minutely verrucose or warty surface.