Placed in the Apiaceae (Umbelliferae) in Michigan Flora. Quite different from all our other Araliaceae and sometimes placed in its own family, Hydrocotylaceae.
1. Petioles attached near center of leaf blade (leaves peltate).
H. umbellata
1. Petioles marginal, attached at sinus of a reniform blade.
2. Umbels sessile or subsessile.
H. americana
2. Umbels on long peduncles.
H. ranunculoides
All species found in Hydrocotyle
Citation:
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. December 15, 2018. https://michiganflora.net/genus.aspx?id=Hydrocotyle.