It has been noted that spore characters are diagnostic for separating various North American taxa of Dryopteris (Crane, 1953) .. Professor Irene Manton (see Manton, 1950), University of Leeds, and Dr. Stanley Walker, University of Liverpool, who have worked on the cytology of diploid and tetraploid specimens of British and European D. dilatata (Hoffm.) A. Gray, report it difficult to distinguis...
