If a plant once grew somewhere, but no longer does, should we still include those places in its distribution? How long ago did it have to disappear for it to be dropped from a location? 200 million years? Fossils of interrupted fern have a panboreal distrubution going back to the Triassic period. Its present distribution is limited to eastern North America and eastern Asia. I always figured this was named interrupted fern because the fertile fronds have sterile leaflets both below and above these fertile ones. Now it could be because of its interrupted modern distribution? Or because of its interrupted classification? This has been called Osmunda for a long time. Within the last three years it has become Claytosmunda or Osmundastrum. We seem to be in an intermediate phase of figuring it out. Presently this large fern grows in damp places in AL, AR(T), CT, DE, GA, IA, IL, IN, KY, MA, MD, ME, MI, MN, MO, MS, NC, NH, NJ, NY(V), OH, PA, RI, SC, TN, VA, VT, WI, WV, LB, MB, NB, NF, NS, ON, PE, QC, and on SPM. Baraga Co MI, 7/13/14. Royal fern family, Osmundaceae.