Hab.—In one form or another, this species occurs in America from Greenland to Peru, throughout Europe and Asia, in parts of Africa, and in many islands of the ocean. The ordinary European form corresponding to Moore’s plate XIV has been collected in British Columbia by Dr. Lyall, in Keweenaw Peninsula of Northern Michigan by Dr. Robbins, and in the mountains of Colorado by Messrs. Hall & Harbour and Mr. Brandegee. Var. _incisum_ was found at the base of calcareous rocks at Royston Park, Owen Sound, Ontario, Canada, by Mrs. Roy, and in the mountains of Colorado by Dr. Scovill, for one of whose specimens I am indebted to D. A. Watt, Esq., of Montreal. Fragments of apparently the same form have been received from Dakota. The Californian plant mentioned in Plantæ Hartwegianæ, p. 342, is better regarded as a form of _Aspidium rigidum_. Var. _paleaceum_ has not been found in either Canada or the United States, but is well known in Mexico, in Europe, in Southern Asia, in the Hawaiian Islands, etc.
Description:—This fern has a stout, usually ascending, but sometimes erect, very chaffy root-stock, very much like that of the species last described. It sometimes rises a little above the surface of the ground, forming a short trunk.
The stalks seem to vary a good deal in length, being sometimes only two or three inches long, and at other times over a foot. They are clustered at the growing end of the root-stock, and their bases, which remain long after the rest has perished, are consolidated with the root-stock. The stalks are always more or less chaffy, the chaff mainly confined to the lowest portion in some plants, and in others following the stalk and the rachis to the apex of the frond. The largest scales are sometimes fully an inch long. They are narrowly lanceolate-acuminate, distantly ciliate-denticulate on the margin, and composed of narrow but somewhat sinuous cells. Mixed in with them are smaller scales, from two to four lines long, and more distinctly ciliate-toothed. The color of the scales is different in different specimens, varying from bright golden-brown to ferruginous-brown with a darker spot at the base, and from this to nearly black, especially in the sub-tropical and tropical forms of var. _paleaceum_. Such specimens are sometimes fairly shaggy with the abundance of scales, which are also found, decreasing in number and in size, on the midribs of the pinnæ, and even on the lower surface of the segments. The usual number of fibro-vascular bundles is seven.