4. Diphasiastrum sitchense (Ruprecht) Holub, Preslia. 47: 108. 1975.
Sitka club-moss, lycopode de Sitka
Lycopodium sitchense Ruprecht, Beitr. Pflanzenk. Russ. Reiches 3: 30. 1845
Horizontal stems on substrate surface or shallowly buried, 1--2.7 mm wide; leaves appressed, broadly lanceolate, 1.8--3.2 X 0.5--1 mm, apex blunt. Upright shoots clustered and branching mostly at base, 5.5--17.5 cm; leaves appressed, broadly lanceolate, 1.8--3.2 X 0.5--1 mm, apex acuminate. Branchlets dark green, somewhat shiny, round in cross section, 1.7--2.5 mm wide, annual bud constrictions inconspicuous. Leaves on branchlets monomorphic, 5-ranked, not overlapping, appressed to spreading-ascending, incurved, free portion of blades 3.4--5.6 X 0.4--0.9 mm, widest at middle, apex sharply pointed. Peduncles absent or rarely 1 cm. Stalks absent. Strobili solitary on upright shoots, 4.5--38 X 3--5 mm, gradually narrowing to rounded tip. Sporophylls deltate, 1.8--3.6 X 1.7--2.8 mm; apex rounded. 2 n = 46.
Alpine meadows, open rocky barrens, conifer woods; 200--2000 m; Greenland; St. Pierre and Miquelon; Alta., B.C., Man., N.B., Nfld., N.S., Ont., P.E.I., Que., Sask., Yukon; Alaska, Idaho, Maine, Mont., N.H., N.Y., Oreg., Vt., Wash.; Asia in Kamchatka, Japan.
The mature shoots in Diphasiastrum sitchense resemble the juvenile phases of the other species. The unique, round, 5-ranked leaves may represent an early developmental state.
The hybrid Diphasiastrum alpinum X sitchense is very rare. It is known from Greenland, British Columbia, Newfoundland, Montana, Oregon, and Washington. Specimens of D . sitchense from Greenland, Newfoundland, and Washington cited by J. H. Wilce (1965) are actually this hybrid.