Sinapis

1. Fruit and even mature ovary densely hispid with spreading to ascending hairs; beak of fruit very flat, as long as the body when ripe.

S. alba

1. Fruit and ovary glabrous (or sometimes with a few short reflexed hairs); beak rarely over half as long as the body, 4-angled to terete.

S. arvensis

All species found in Sinapis

Sinapis albaWHITE MUSTARD 
Sinapis arvensisCHARLOCK, WILD MUSTARD 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. December 13, 2017. http://michiganflora.net/genus.aspx?id=Sinapis.