1. Pistils in a dense spherical head; uppermost flowers mostly staminate, with the stamens numerous; leaves unlobed or sagittate.
1. Pistils in a single ring on a flattish receptacle or few in a tiny loose head; flowers all bisexual, with 6 (–9) stamens; leaves never lobed.
2. Plants nearly always more than 10 cm tall; achenes ca. 1.5–3 mm long, flattened.
2. Plants less than 10 cm tall; achenes ca. 1–1.3 mm long, plump.
All species found in Alismataceae
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. July 22, 2019. https://www.michiganflora.net/family.aspx?id=Alismataceae.