Isoetes lacustris (lake quillwort or Merlin's grass) is a boreal quillwort native on both sides of the northern Atlantic Ocean. In Europe, it is distributed from Poland west to northeastern France, throughout Scandinavia, the west and north of the British Isles, the Faroe Islands and Iceland. In the North America, it occurs in the New England states of Maine, Vermont, New Hampshire Rhode Island and Massachusetts, and in Canada in provinces of New Brunswick and Nova Scotia. It was discovered by Johannes Reinke.