Sphagnum angstromii

Sphagnum angstromii Hartm. f.; Hartm. Skand. Fl ed. 7. 399. 1858.
Plants fairly robust, yellowish-green. Wood-cylinder yellowish-green; cortical cells of the stem in 3-4 layers, large with thin walls, the outer cells irregularly quadrilateral to pentagonal, sometimes about as wide as long, without fibrils, rarely with a pore near the upper end of the cell: stem-leaves of medium size, lingulate, slightly concave, somewhat lacerate across the apex, the border narrow and indistinct above, much broadened toward the base where the walls of its cells are strongly pitted; hyaline cells rhomboidal, narrow below, in the apical part nearly as wide as long, without fibrils or divisions, their membrane on the outer surface almost entirely resorbed in cells of the apical part, the gaps decreasing in size toward the base, passing into longitudinal membrane-pleats, on the inner surface more nearly intact, resorbed in 2-3 rows of cells of the immediate apex, with occasionally very small gaps in the ends of cells further down, and with longitudinal membrane-pleats throughout: branches in fascicles of 5, 2 or 3 stronger, spreading, their cortical cells in a single layer, the retort-cells with an inconspicuous neck, commonly a second shorter one above the first : branch-leaves closely imbricate when dry, broadly ovate, very strongly concave, with a broadly truncate toothed apex (about 10 teeth across the apex), the border of 1-2 rows of narrow cells, entire except in the immediate vicinity of the apex; hyaline cells fibrillose. linear-rhomboidal, 6-8 times as long as wide at the base, shorter in the immediate apex, on the inner surface with a few mediumsized pores in the cell-angles and near the commissures, fairly numerous only in cells near the outer edge, where they number up to 8 per cell, rapidly diminishing in number inwardly and after a few rows of cells lacking entirely, on the outer surface the pores more numerous, similar or somewhat elliptic, 6-14 per cell: chlorophyl-cells truncately elliptic in section, exposed about equally on both surfaces, the lumen elliptic, exactly central; hyaline cells slightly convex on both surfaces, rather more so on the outer where the convexity is one sixth to one fifth of the diameter of the cell.
Dioicous. Antheridia on spreading branches; antheridial leaves much smaller than the others, not strongly pigmented, yellowish-green, saccate at the base, where the fibrils are considerably reduced or lacking. Fruiting branches erect, short; perichaetial leaves lingulate, broadly rounded and often rent at the apex, showing boih kinds of cells in the upper middle portion where the hyaline cells are small, undivided, without fibrils, their membrane on the inner surface entire, on the outer surface much resorbed: capsule dark-brown: spores brown-yellow, about 25 /i in diameter, very minutely granular-roughened.
Type locality: Lapland.
Distribution: Alaska and Yukon; also in arctic and subarctic Europe and Siberia.