Flora of North America species comparison

D. F. M. Brown (1964) hypothesized that tetraploid Woodsia obtusa might be an autopolyploid derived from W. oregana. Recent isozyme and spore ornamentation studies indicate, however, that these species are not closely related, and the discovery of a diploid cytotype of W. obtusa suggests a different (albeit autopolyploid) origin for this taxon (M. D. Windham 1993). Tetraploid subsp. obtusa crosses with diploid subsp. occidentalis; the resulting triploids are sterile and have malformed spores. It also hybridizes with W. oregana subsp. cathcartiana to form the sterile tetraploid hybrid known as W. × kansana Brooks.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

The family Dryopteridaceae has been variously circumscribed; it is here delimited in a manner similar to that of R. M. Tryon and A. F. Tryon (1982) but with the inclusion of Nephrolepis. In many works, the family has gone under the illegitimate name Aspidiaceae. Some authorities define Dryopteridaceae more narrowly, to exclude Athyrium, Deparia, Diplazium, Cystopteris, and Gymnocarpium (Athyriaceae or Woodsiaceae), Woodsia (Woodsiaceae), Lomariopsis (Lomariopsidaceae), Nephrolepis (Nephrolepidaceae or Davalliaceae), Onoclea and Matteuccia (Onocleaceae), and Ctenitis and Tectaria (Tectariaceae). Characteristics holding Dryopteridaceae (as circumscribed here) together include the bilateral, monolete spores, often broadly winged perispore, absence of needlelike hairs, scaly stem and petiole bases, abaxial (nonmarginal) sori, base chromosome number of 40 or 41 (also 38 and 39 in Woodsia, 37 in Onoclea, 42 in Cystopteris), and usually indusiate sori. Loss of indusium, dimorphism, areolate venation, and reduced blade dissection have occurred repeatedly along many evolutionary lines in Dryopteridaceae, and in general these characteristics are often not very useful in delimiting genera or assessing intergeneric relationships.

In some genera, especially Phanerophlebia and Polystichum, the blade bears very narrow scales (sometimes called microscales) that resemble uniseriate hairs. These scales may be only one or two cells wide. Every intergradation exists between these filiform microscales and more typical, wider scales, and the two types are the same color, generally tan to brownish. Microscales are probably not homologous with true hairs, which may be either unicellular or multicellular, uncolored or sometimes reddish (as in Tectaria and Ctenitis), glandular (as in Woodsia) or not. Hairs in Dryopteridaceae, if present at all, are generally readily distinguishable from the needlelike, transparent ones found in Thelypteridaceae.

Genera ca. 60, species perhaps exceeding 3000 (18 genera, 79 species in the flora).

(Discussion copyrighted by Flora of North America; reprinted with permission.)