Abstract

With both conventional and modern techniques the author undertakes to determine the proper systematics of the lady ferns of the genus Athyrium found in North America north of Mexico. Ataximetric comparison of ninety-nine characters by the computer program working on a non-statistical optimazation measure of cluster analysis (Rubin, 1966) is used to test the validity of conclusions reached by other methods. A semi-objective graphic evaluation of their phylogenetic relationship is considered by the ground plan method (Wagner, 1961). Both analyses produce results essentially similar to those reached by biosystematic studies, namely that there are two distanly related lineages in Athyrium, one comprising the ailvery althyrium and glade gern, the other the common and the alpine lady ferns. The glade fern is found to be a highly specialized member of its group, as is also the American alpine lady fern. Thus, there are four consisting of three sunspecies with geographically distinct ranges.