oak fern, Gymnocarpium dryopteris

Oakfern originated as a cross between two other species of Gymnocarpium. In the process, it wound up with an extra set of chromosomes. One of those parents now only grows in a limited area of the Appalachians. The other is limited to the Pacific northwest and far northeastern Asia. But their polyploid offspring? Boom! Superfern! Oak fern is circumboreal, growing in all of northern Eurasia, and in AK, AZ, CO, CT, IA, ID, IL, MA, MD, ME, MI, MN, MT, ND, NH, NJ(S1), NM, NY, OH, OR, PA, RI, SD, UT, VT, WA, WI, WV, WY, all of Canada, and on GL and SPM. Cheboygan Co MI, 7/11/14. Fragile fern family, Cystopteraceae.