1. Stems with trifid spines ca. 1 cm or more long at the nodes; leaf blades tapering to a short petiole.
1. Stems spineless; leaf blades ± cordate, mostly about 1–2 times as long as their petioles.
All species found in Xanthium
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. May 24, 2017. http://michiganflora.net/genus.aspx?id=Xanthium.