Diphasiastrum digitatum
Preslia 47: 108. 1975.
Horizontal stems on substrate surface, 1.3–2.7 mm wide; leaves appressed to ascending, linear to narrowly lanceolate, 1.8–4.5 × 0.6–1.2 mm, apex acute, scarious, often lost. Upright shoots 15–50 cm, branching regularly successively to 3 times; leaves appressed with decurrent base, subulate, 1.8–3.5 × 0.6–1 mm, apex acute. Branchlets flat in cross section, narrowly bladelike, 2.8–3.9 mm wide, annual bud constrictions very rare; underside dull, pale, flat; upperside green, flat, shiny. Leaves of branchlets 4-ranked; upperside leaves appressed, linear-lanceolate, free portion of blade 0.7–1.5 × 0.5–0.9 mm; lateral leaves appressed to spreading (spreading especially in juvenile stages), 3.1–5.5 × 1–2 mm; underside leaves very weakly developed, spreading, narrowly deltate, 0.3–1 × 0.3–0.7 mm, apex pointed. Peduncles mostly 2, 4.4–12.5 × 0.1–1.3 cm; leaves usually somewhat whorled, linear-lanceolate to nearly filiform, 2–3.3 × 0.5–0.9 mm, apex blunt to acute. Stalks mostly pseudowhorled, 2-forked, forks basal. Strobili 2–4 per upright shoot, 14–40 × 2–3 mm exclusive of elongate sterile tip; sterile tips to 11 mm (occurring on ca. 50% of specimens), apex blunt to acute if sterile tip is absent. Sporophylls deltate, 1.7–2.6 × 1.8–2.8 mm, apex abruptly tapering. 2n = 46.
Habitat: Coniferous and hardwood forests and second growth, shrubby or open fields
Elevation: 0–1500 m
Distribution
St. Pierre and Miquelon, N.B., Nfld., N.S., Ont., P.E.I., Que., Ala., Ark., Conn., Del., D.C., Ga., Ill., Ind., Iowa, Ky., Maine, Md., Mass., Mich., Minn., Mo., N.H., N.J., N.Y., N.C., Ohio, Pa., R.I., S.C., Tenn., Va., W.Va., Wis.
Discussion
An endemic in eastern North America, Diphasiastrum digitatum is the most abundant species of Diphasiastrum on the continent, much used for decoration as wreaths. It was long confused with the circumboreal D. complanatum.
Selected References
None.