1. Involucre a spiny bur enclosing much or all of the spikelets, the whole readily disarticulating.
C. longispinus
1. Involucre of slender bristles ca. 2–4 cm long subtending but not concealing the spikelet.
C. purpurascens
All species found in Cenchrus
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=Cenchrus.