Biomorphological Features of North American Homophyllous Water Crowfoot Ranunculus longirostris (Batrachium, Ranunculaceae)

Abstract

Features of biomorphology of homophyllous water crowfoot Ranunculuslongirostris (Batrachium, Ranunculaceae) occurring in North America were studied. From the generally similar group of the rigid-leaved water crowfoots (the R. circinatus group), R. longirostris is distinguished by the presence of a long internode before the first flower (the ratio of leaf and internode lengths is 1 : 5), persistent stipules throughout the shoot, a “true” dichotomy in the structure of inflorescences, conical nectar pits and fruits with a long persistent beaks. The latter feature distinguishes this species from the rest of the water crowfoots. An analysis of the inflorescence variants of aquatic, semiaquatic, and terrestrial Ranunculus shows that R. longirostris had initial dichasia branching that is almost unique within Batrachium, as well as an additional multiaxial structure in the lateral axes of the inflorescence which is known for some semiaquatic and terrestrial Ranunculus species. The data demonstrate the specific position of R. longirostris in Batrachium and contribute to the evidences of the close relationship between Batrachium and other Ranunculus.