| Gymnocarpium jessoense is a rare fern, similar in appearance 
                to the common G. dryopteris. Fronds are usually less than 
                40 cm long. The blade ranges from 3-14 cm long and is shorter 
                than the stipe. The blade is broadly triangular, 2- pinnate-pinnatifid 
                and ternate (divided into three roughly equal branches at the 
                base). Sori are round, located on the underside of the blade and 
                there is no indusium. The horizontal stems are elongate so leaves 
                are not densely aggregated.  There are three similar species in this genus in Wisconsin, distinguished 
                as follows. The abaxial (under) surface of rachis and blade of 
                G. jessoense are clearly glandular and the adaxial (upper) 
                surface is glabrous. G. dryopteris is glabrous on both 
                surfaces and G. robertiana is glandular on both surfaces. 
                Basal pinnae of G. jessoense are often curved toward 
                the tip of the frond, and those of G. robertianum are usually 
                straight and not pointing toward the tip of the frond. The reader 
                is directed to the Flora of North America, upon which this description 
                is based. G. jessoense is found primarily from Wisconsin, Minnesota 
                and Ontario, west through Canada to Alaska. Disjunct locations 
                are also known from eastern Canada and the northeastern U.S. It 
                is listed as a "special concern" species in Wisconsin 
                where it has been recorded only from Bayfield County, often on 
                or near acidic rocks. |