Protrusa? So what protrudes on a fern? You have to kind of mess around in the dirt at the bases of plants to see. After the rhizome sends up a season's fronds, it grows a little farther. Finding this protrusion is the absolute sure way to identify this species. This is a relatively small plant that you will mostly see in the spring. You may find it springing up around spring ephemeral wild flowers. Sort of like filler in a flower arrangement. Could that be how our senses learned to appreciate the effect of ferns nicely placed around our arrangements? Maybe those carefully placed flowers end up more natural than we realize? Unlike most Cystopteris, you will see these ferns growing on forest floors. Others are more likely on rocks. Grub around them if you're in AL, AR, CT, DE, FL, GA, IA, IL, IN, KS, KY, LA, MA, MD, MI, MN, MO, MS, NC, NE, NH, NJ, NY, OH, OK, PA, SC, TN, TX, VA, WI, WV, and ON. Lenawee Co MI, 5/18/13. Fragile fern family, Cystopteraceae.