Burgess, Trans. Roy. Soc. Can., iv., sect. iv., 12.
One of the rarest of American ferns, and is found growing in tufts in wet shade on limestone rocks. Only three stations are known in Canada. Woodstock, N.B. (Sutton, Jack.) Abundant on limestone debris under the cliffs at Sydenham Falls and other localities around Owen Sound, Ont. (Mrs. Boy.) On Guelph dolomites, Little Sau-River, Durham, Grey Co., Ont. (H. M. Ami.) It is a very variable species and three of the forms, which have been known, respectively, as vars. marginatum, ramosum, and multifidum, were collected near Woodstock, N.B., by Mr. Jack.