Pteridaceae

1. Blade without a central axis, forked into two equal parts, each with an arching axis.

Adiantum

1. Blade with a single central axis.

2. Petioles green to straw-colored for at least the upper 1/3 to1/2, rachis green; leaves dimorphic, the fertile longer than the sterile and with narrower segments.

Cryptogramma

2. Petioles and rachis dark brown to almost black throughout; leaves essentially uniform.

Pellaea

All species found in Pteridaceae

Adiantum pedatumMAIDENHAIR FERN 
Cryptogramma acrostichoidesAMERICAN ROCK-BRAKE 
Cryptogramma stelleriSLENDER ROCK-BRAKE 
Pellaea atropurpureaPURPLE CLIFF-BRAKE 
Pellaea glabellaSMOOTH CLIFF-BRAKE 

Citation:

MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. June 21, 2018. https://michiganflora.net/family.aspx?id=PTERIDACEAE.