Jensen's Sphagnum

This species is characterized by having slender, brownish plants with small stem leaves and elongate branch leaves (twice as long as stem leaves), and by having linear-rhomboidal hyaline cells of branch leaves with commissural pores on both surfaces.

Sporophytes of Sphagnum jensenii are uncommon. For more information, see discussion under 23. S. annulatum.

Plants rather stout, 10–15 cm high, whitish green, capitula often brown, in compact tufts. Stem cortex in 1–2 layers, hyaline cells relatively thick-walled, poorly differentiated from inner cortical layers (4–5 layers) and central cylinder; central cylinder yellowish. Stem leaves 0.8–1.0 mm long, triangular to triangular-ligulate, nearly as long as wide, rounded truncate, dentate at the apex; borders narrow above, slightly widened below; hyaline cells linear-rhomboidal, rarely divided, without fibrils and pores, or rarely with fibrils and pseudopores on both surfaces in the upper cells. Branches in fascicles of 4, with 2 spreading, ca. 1.5–2.0 cm long. Branch leaves 2.2–2.4 mm × 0.5–0.9 mm, imbricate, sometimes secund, narrowly ovate-lanceolate, twice as long as stem leaves, gradually narrowed to a blunt and dentate apex; margins bordered by 2–3 rows of linear cells, entire, involute; hyaline cells linear-rhomboidal, densely fibrillose, with medium-sized, ringed pores on the ventral surface, with small, rounded, unringed pores in commissural rows on the dorsal surface; green cells in cross section triangular, exposed on the dorsal surface, enclosed by convex hyaline cells on the ventral surface. Dioicous; antheridial branches brownish. Perichaetial leaves ovate, broadly bordered. Spores pale yellowish, smooth, ca. 30 µm in diameter.

Plants moderate-sized to robust, weak-stemmed; pale brown to chestnut brown; capitulum flat-topped and generally 5-radiate, branches straight to somewhat curved, terminal bud often visible. Stems pale green to brown, superficial cortex of 2 layers of thin-walled and well differentiated cells. Stem leaves triangular, ovate-triangular to triangular-lingulate, 1-1.3 mm; appressed to spreading; apex obtuse, hyaline cells usually fibrillose near apex. Branches straight to somewhat curved, leaves moderately elongate at distal end. Branch fascicles with 2 spreading and 1-2 pendent branches. Branch stems green, cortex enlarged with conspicuous retort cells. Branch leaves ovate-lanceolate; usually more than 2 mm; straight; weakly undulate and slightly recurved when dry, margins entire; hyaline cells on convex surface with numerous small free pores in proximal ²/3 of leaf and in apical region with numerous pseudopores along commissures, on concave surface with numerous round free pores; cells relatively long and narrow in basal region, much longer than in mid region; chlorophyllous cells triangular in transverse section and well-enclosed on concave surface. Sexual condition dioicous. Spores 29-33 µm; both surfaces very smooth; proximal laesura long, more than 0.6 spore radius.

Disribution. China, Japan, Central Asia, Russian Far East, Europe, and North America.

Habitat: in peatland under coniferous forests or on wet rocks near streams.

Sphagnum annulatum var. porosum (Warnstorf) W. S. G. Maas