I'm gradually getting better at fern identification, although, for reasons that escape me, I'm hardly a pro, despite a fair amount of study. But this one, which I knew instantly to be a Marsh Fern, is among the Pteridophytes that I can rattle off easily. The key to getting this one right was a gift from two crackerjack botanists, Doug McGrady and Brian Maynard, who led a Rhode Island Wild Plant Society walk I attended last August and who were both gifted teachers. They told me that the important characteristic fieldmark of this common fern, besides its penchant for wet, sunlit meadows, was its habit of, when fertile, rolling the edges of its twice-cut leaves over its collection of spores. This presumably keeps the reproductive elements of Thelypteris palustris well protected and ready, when it's time, for the wind and water to take the spores to new and, perhaps, greener pastures.