Prototype quillwort is endemic to New England and far eastern Canada (New Brunswick and Nova Scotia). It is very rare in New England, where it is found only in cold clear lakes in Maine.
velum covering less than half the sporangium and leaves pliant and curling at the tip (vs. I. prototypus, with the velum covering the entire sporangium and leaves very rigid and straight to the tip).
prototype quillwort. ME. Cold, clear lakes with mineral substrate.