Noun | 1. | ![]() fern genus - genera of ferns and fern allies family Pteridaceae, Pteridaceae - one of a number of families into which the family Polypodiaceae has been subdivided in some classification systems; Pteridaceae is itself in turn sometimes further subdivided rock brake - dwarf deciduous lithophytic ferns American parsley fern, American rock brake, Cryptogramma acrostichoides - rock-inhabiting fern of northern North America growing in massive tufts and having fronds resembling parsley |