Spinulum

1. Longest leaves (5.5–) 6–9 mm long, spreading or even ±reflexed, usually at least obscurely toothed near the apex.

S. annotinum

1. Longest leaves 4.3–5.5 (–6) mm long, all but the lowest ascending, usually entire.

S. canadense

All species found in Spinulum

Spinulum annotinumSTIFF CLUBMOSS 
Spinulum canadenseCLUBMOSS 

Citation:

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