Cryptogramma stelleri (Gmel.) Prantl ex Engler
Habitat: Cool and shaded calcareous rock or springy slopes. [Rocky summits and outcrops (non-forested, upland); Hardwood to mixed forest (forest, upland); Non-tidal rivershore (non-forested, seasonally wet)]
Range: Labrador to Alaska, south to New Brunswick and locally to West Virginia, Illinois, and Washington.
Aids to Identification: This low-creeping fern is tiny (less than 8 cm), fragile, and almost translucent. The small delicate fern is best identified by its dimorphic (i.e. having 2 forms) leaves. As the illustration shows, the vegetative leaves have flat, lobed to divided leaflets. The spore-bearing leaves are more narrow and revolute-margined (the edges curl under). The spores are borne in a continuous band along the edge of the leaflet segments.
Ecological characteristics: In Maine, slender cliffbrake is typically found growing on rock outcrops and vertical ledges in deep moist shade.
Phenology: Fruits August - September.
Synonyms: None noted.
Known Distribution in Maine: This rare plant has been documented from a total of 7 town(s) in the following county(ies): Aroostook, Oxford, Piscataquis, Somerset.
Reason(s) for rarity: Disjunct from primary range; habitat naturally scarce.
Conservation considerations: Known populations are in fairly remote locations not particularly vulnerable to human activities. A few historic populations have not been recently relocated.