Biosystematics of the Genus Hydrophyllum L. (Hydrophyllaceae)

Hydrophyllum is a group of mesophytic herbs occurring in two disjunct groups in North America. The genus is a natural taxonomic entity with the constituent species showing low levels of variability. Morphological similarities of the disjunct species suggest a close affinity between H. tenuipes and H. virginianum and a lesser, yet distinct, affinity between H. occidentale and H. macrophyllum . Biosystematic studies that included herbarium comparisons, field descriptions, artificial hybridizations, chromatographic studies, and electrophoretic analyses characterize the interrelationships of the various species.