Flora of North America species comparison

Gymnocarpium dryopteris is a fertile allotetraploid species that arose following hybridization between G. appalachianum and G. disjunctum (see reticulogram). Its wide distribution over much of the north temperate zone has provided ample opportunity for secondary contact between G. dryopteris and each of its diploid parents, thereby resulting in a wide-ranging composite of abortive-spored triploid crosses (G. disjunctum × G. dryopteris and G. appalachianum × G. dryopteris). These relationships are shown on the diagram. Sterile triploid plants are not restricted only to areas where the range of the tetraploid overlaps with that of either diploid. Their broad distribution could be explained in part by their spores, which are of two types: malformed, black, and with very exaggerated perispores, or round with extensive netted perispores (K. M. Pryer and D. M. Britton 1983). The latter spore type is capable of germination and presumably permits the plants to reproduce apogamously. The name G. × brittonianum (Sarvela) Pryer & Haufler has been applied to the G. disjunctum × G. dryopteris hybrid formula (K. M. Pryer and C. H. Haufler 1993). The type of G. × brittonianum has aborted and round spores, and leaves that strongly resemble those of G. disjunctum. They are large, 3-pinnate-pinnatifid, and the second and third pairs of pinnae are sessile with basal basiscopic pinnules markedly longer than the basal acroscopic pinnules. Sterile triploid plants with a morphology similar to the type of G. × brittonianum are frequent. The biology of both of these cryptic hybrid taxa needs further study, which should lead to detailed morphologic descriptions and distribution maps.

Gymnocarpium dryopteris also hybridizes with both G. jessoense subsp. parvulum and G. robertianum.

(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.)