Shoots erect, indeterminate, 8--12 cm, becoming short-decumbent; leaves of mature portion slightly smaller than leaves of juvenile portion (more pronounced in sun form); indistinct annual constrictions present (more pronounced in shade form); juvenile growth erect. Leaves spreading-ascending (shade) to appressed-ascending (sun) in mature portion, more reflexed in juvenile portion, green (shade) to yellow-green (sun), lustrous; largest leaves triangular, widest at base, 4--7.5 mm; smallest leaves lanceolate, 3.5--5 mm; margins almost entire, papillate; stomates on both surfaces, numerous on adaxial surface, 30--90 per 1/2 leaf. Gemmiferous branchlets produced in 1 pseudowhorl at end of annual growth; gemmae 4--5 X 3--4.5 mm, lateral leaves 1.5--2 mm wide, broadly acute. Spores 29--37 µm. 2 n = 268. Terrestrial in sandy borrow pits, ditches, lakeshore swales, and conifer swamps, rarely on acidic, igneous rock or calcareous coast cliffs; 0--700 m, rarely to 1600 m; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Conn., Maine, Mass., Mich., Minn., N.H., N.Y., Ohio, R.I., Vt., Wis.; Europe; Asia. Plants from Greenland formerly identified as Huperzia selago are H . appalachiana .
Horizontal stems short; erect or ascending stems 6-20 cm, 2-3 mm thick (excl. lvs); lvs in ca 8 ranks, subulate or triangular-subulate, broadest at or near the base, gradually acuminate, entire, glossy, 3-5 x 0.6-0.8 mm, often with axillary gemmae; sporophylls resembling the vegetative lvs, borne in zones at the beginning of each season's growth (or all the lvs eventually becoming fertile); sporangia broadly reniform, 1-1.5 mm wide; spores 32-38 microns in diameter, the sides concave, the commissural faces smooth, the outer face papillate, the commissures not in furrows; high polyploid, ca 2n=268. (Huperzia s.) The circumboreal var. selago, with ±spreading lvs, occurs in moist, often rocky and wooded places s. to Mass., N.Y., Wis., Minn., and in the mts. (but not at the highest elevs.) to N.C. and Tenn. Alpine and subalpine plants of exposed sites from Nf. to N.Y., and s. irregularly in the highest mts. to N.C. and Tenn., with more tufted, short stems and erect-appressed lvs, have been associated (perhaps incorrectly) with the European var. appressum Desv.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.