Plants moderate to large-sized, dense and compact, pale green, brownish white, golden brown to variegated golden brown, can be reddish in rocky seep habitats; forms small, tufted compact cushions. Stems brown. Stem leaves small, 0.3-0.7 mm, triangular-lingulate with broad rounded apex, Branches short, crowded, and unranked. Branch fascicles 4-6 branches per fascicle, 2-3 spreading and 2-3 pendent, but plants frequently unbranched in young clones. Branch leaves large, 1.4-3 mm, semi-squarrose to squarrose, ovate and abruptly involute in distal portion, appearing cucullate with toothed apex, usually no more than 6 teeth; hyaline cells with 5 or more ringed, round to elliptical pores on convex surface, numerous pseudopores on concave surface with 3-ringed corner pores occurring in 3s at adjacent cell angles; chlorophyllous cells elliptic in transverse section, entirely included by hyaline cells, slightly nearer to convex surface. Sexual condition monoicous. Capsule with abundant pseudostomata. Spores 25-35 µm; finely papillose on proximal surface, coarsely papillose on distal surface with raised Y-mark sculpture; proximal laesura short, 0.3-0.5 spore radius.
Plants stout in dense or compact tufts, grayish to yellowish green or tinged with pinkish red. Stem cortex in 2–3 layers, hyaline cells large, thin-walled, without fibrils, with a single pore; central cylinder yellowish brown. Stem leaves 0.50–0.55 mm × 0.6 mm, triangular-ligulate, with rounded, involute, often lacerate apices; borders clearly widened at leaf base, occupying about 1/6 leaf width; hyaline cells rhomboidal, not divided, without fibrils, with pores only on the ventral surface. Branches short, stout, and crowded in fascicles of 4–6 with 2–3 spreading. Branch leaves 1.6–2.6 mm × 0.8–1.6 mm, broadly ovate, several times larger than stem leaves, concave with involute-concave apex; borders indistinct, sometimes denticulate along margins; hyaline cells densely fibrillose, with numerous pseudopores, 2–3 pores at the corners of each cell on the ventral surface, few to numerous rather larger pores at the ends on the dorsal surface; green cells in cross section small, narrowly oval to elliptic, centrally located or slightly widened toward the dorsal surface, enclosed by hyaline cells on both surfaces. Monoicous. Perigonial leaves not differentiated. Perichaetial leaves broadly ovate to oblong ovate, subsecund, concave. Spores yellowish brown, 32–35 µm in diameter.
Sphagnum compactum var. imbricatum Warnstorf; S. rigidum (Nees & Hornschuch) Schimper
Sphagnum compactum var. imbricatum Warnst., Bot. Gaz. 15: 226. 1890.
Holotype for Sphagnum compactum var. expositum Maass
Catalog Number: US
Collection: Smithsonian Institution, National Museum of Natural History, Department of Botany
Preparation: Pressed specimen
Collector(s): C. F. Reed
Year Collected: 1964
Locality: Rt. 308, 5 mi. SE of Lewiston., Bertie, North Carolina, United States, North America
Holotype: Maass, W. 1966. Nova Hedwigia. 12 (1/2): 91.