Woodsia glabella R. Br. ex Richards.
Habitat: Thin moss or humus on calcareous cliffs, often at crests of shaded cliffs. [Rocky summits and outcrops (non-forested, upland)]
Range: Labrador to Alaska, south to New Brunswick, northern New England, northern New York and British Columbia. Also in Greenland and arctic and alpine Europe and Asia.
Aids to Identification: Cliff ferns (Woodsia) are largely slender ferns of ledges, cliffs, and talus slopes. They are recognized by their distinctive indusia and petioles. Cliff ferns have an inferior indusium (i.e., positioned under the sporangium) that is lacerate into slender filaments. The petiole bases have a swollen node where the upper part of the petiole is articulated. All the petioles break off at the same point so that the persistent leaf stalks are all the same length. Woodsia glabella is the smallest cliff fern in Maine. Its leaf blades are only 1-1.5 cm wide. This plant lacks hairs that the other cliff ferns, including W. alpina, posess. Other useful identifying features are the flabellate (fan-shaped) lower leaflets and sessile glands found over the leaf blade.
Ecological characteristics: Ecological relationships in Maine are not well known.
Synonyms: Woodsia alpina (Bolton) S.F. Gray var. glabella (R. Br. ex Richards.) D.C. Eat.; Woodsia hyperborea R. Br. var. glabella (R. Br. ex Richards.) Watt.
Known Distribution in Maine: This rare plant has been documented from a total of 8 town(s) in the following county(ies): Aroostook, Oxford, Penobscot, Piscataquis, Somerset, Washington.
Reason(s) for rarity: Southern limit of its range; suitable habitat is scarce.
Conservation considerations: Populations are small and therefore vulnerable to the vagaries of small populations like random fluctuations or localized disturbance events. Known populations are not particularly vulnerable to human activities.