Ophioglossum pusillum Raf.
Habitat: Acid swales, wet thickets, shores, damp, sterile pastures [Non-tidal rivershore (non-forested, seasonally wet). Open wetland, not coastal nor rivershore (non-forested wetland)]
Range: New Brunswick south to North Carolina, west to Nebraska and California, north to North Dakota and British Columbia.
Aids to Identification: Northern adder's-tongue is a fern with a non-fern-like appearance. It is an inconspicuous plant with a single, simple sterile blade. The blade is oval-elliptical to spatualate in shape (up to 10 cm long and up to 3.2 cm wide). Sporangia are borne on a compact, linear sporophore (stalk that bears spores).
Ecological characteristics: Found mostly in wet swales and bogs. Very inconspicuous.
Phenology: Leaves appear mid-spring.
Synonyms: Ophioglossum vulgatum L. var. pseudopodum (Blake) Farw.
Known Distribution in Maine: This rare plant has been documented from a total of 13 towns in the following counties: Aroostook, Cumberland, Franklin, Hancock, Kennebec, Lincoln, Oxford, Piscataquis, Waldo, York.
Reason(s) for rarity: Unclear; may be under collected due to inconspicuous nature.