A morphological phylogenetic analysis of the angiosperm family Hydrophyllaceae (Boraginales) was performed. Hydrophyllaceae are a group of New World herbs and shrubs with 15 genera and ca. 300 species. In total, ca. 75 morphological characters were scored for 56 terminal taxa, 52 Hydrophyllaceae species and four outgroups in Boraginaceae s.l. The characters, representing vegetative and reproductive structures, were scored from herbarium specimens and from information available in the literature. Scanning electron microscopy of pollen and seeds, added to those already published, were included in this survey. The morphological data are more or less congruent with results of molecular phylogenetic studies of the chloroplast gene ndhF and nuclear ITS region. A combined data analysis produces a well supported phylogeny for Hydrophyllaceae. Characters used to define “higher”-level taxonomic groupings, such as locule number and ovary structure, ovule number, corolline appendages, and growth form are highly homoplasious and it is difficult in many cases to define character states and/or assess homology. Less homoplasious characters that define clades will be presented, including style number, dehiscence type, presence of false germination furrows on pollen, and placentation.

Key words: Boraginaceae, Hydrophyllaceae, morphology, phylogeny