Alismataceae

1. Pistils in a dense spherical head; uppermost flowers mostly staminate, with the stamens numerous; leaves unlobed or sagittate.

Sagittaria

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.

Alisma

2. Plants less than 10 cm tall; achenes ca. 1–1.3 mm long, plump.

Echinodorus

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. March 27, 2017. http://michiganflora.net/family.aspx?id=ALISMATACEAE.