Comparative Morphology of the Genus Hydrocharis L. (Hydrocharitaceae)

A comparative morphological study of Hydrocharis L. species has been carried out. Based on the results of cluster analysis for 77 morphological characters, the isolation of H. chevalieri (De Wild.) Dandy from other members of Hydrocharis L., the autonomy of the Limnobium Rich., and the validity of combining Limnobium and Hydrocharis into the subfamily Hydrocharitoideae Eaton. are demonstrated. Important diagnostic features for species of Hydrocharis are the shape of its apex, the shape and size of its leaf blade, the proportion of honeycomb aerenchyma, the length of petiole, the size of fruits and seeds, and the thickness of pericarpium. Two groups of rosette vegetatively mobile biomorphs are defined: low annual(oligoennial) free-floating turioniferous hydatophytes ( H. morsus-ranae L., H. dubia (Blume) Backer) and medium–high annual(oligoennial) rooting hydrohelophytes ( H. chevalieri (De Wild.) Dandy).