Horizontal stems superficial to slightly subterranean, elongate, rooting at intervals, with distant, yellowish bract-lvs; erect stems dichotomously branched, to 2 dm, the sterile branches flattened and dorsiventral at least distally, 1.5 mm wide, their lvs in 4 ranks, linear- subulate, sharp-pointed, entire, those of the dorsal and ventral ranks appressed, shortly adnate, those of the lateral ranks slightly larger, adnate half their length, with spreading, apically incurved tip; lvs with stomates on both sides; cones 1.5-2.5 cm, 2.5-4 mm thick, solitary or paired on branching peduncles with slightly reduced, appressed, 6-ranked lvs; sporophylls yellowish, broad-based, abruptly narrowed upwards, with scarious erose margins; sporangia and spores as in no. 11 [Lycopodium clavatum L.]; 2n=46. Subalpine woods and meadows; Lab. to Ont., s. to N.Y., Pa., and Mich. Thought to have originated as a hybrid of nos. 13 [Lycopodium sitchense Rupr.] and 15 [Lycopodium tristachyum Pursh], but now stable and fertile.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.