Lady fern (Athyrium filix-femina), also known as the alpine lady fern, is an uncommon plant in babyÖ±²¥app but can be found in 49 out of 50 states, excluding Hawaii, making it one of the most abundant ferns in the U.S. The telltale mark of a lady fern are clusters of reddish or bright green sori, or spore sacs, on the underside of its almost lacy, feathered fronds. These sori identify the filix-femina as a pteridophytes, a group of vascular plants that reproduce by spores rather than seeds.