For reliable determination, mature fruits and plants with well-developed inflorescences are essential. Immature and depauperate collections may be impossible to name. An additional species, Corispermum hookeri, is known from Ontario and could occur in Michigan. Before we realized that there were several entities in Corispermum in the Great Lakes region, mature fruits were not considered essential for collections and some very immature specimens are mapped here based on tentative determinations. See Mosyakin (1995) for more information.
All thee species are native to North America, but none were collected from Michigan before 1900, though much earlier collections of C. pallasii are known from Lake Michigan shores in Wisconsin. It is surely native. Corispermum americanum is also considered native, even though some collections are from weedy sites. All collections of C. villosum are from weedy habitats or urban settings, and it is treated as introduced.
All measurements in the key are from Great Lakes region collections, and may not apply to the species from elsewhere in its range.
1. Fruit wingless, mostly 2–3.2 mm long.
1. Fruit ± winged, 2.4–4.2 mm long.
2. Inflorescences linear, rather loosely flowered; larger fruits 2.4–3.1 mm long (excluding apiculus).
2. Inflorescences narrowly clavate to ovate in outline, densely flowered except at the very base; larger fruits 3.2–4.2 mm long (excluding apiculus).
All species found in Corispermum
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. January 20, 2020. https://michiganflora.net/genus.aspx?id=Corispermum.