Orthothecium lapponicum (Schimp.) C. Hartm., Handb. Skand. Fl.

5. Orthothecium lapponicum (Schimp.) C. Hartm., Handb. Skand. Fl. View in CoL (ed. 10) 2: 29. 1871.

— Brachythecium lapponicum Schimp., Syn. Musc. Eur. 697. 1860. – Figs. 12A–E View K L , 13I–J View Fig .

Description. Plants in loose tufts, rather soft, golden yellow to yellow-brown to bright red, moderately lustrous. Stems to 5 cm long, ± julaceous, simple or occasionally irregularly branched. Leaves imbricate to slightly spreading, ovate, not or hardly decurrent, rather suddenly narrowed to acute or acuminate and mostly recurved apex, strongly concave and not or hardly plicate, 1.0–2.3× 0.5– 0.9 mm; leaf margins narrowly recurved from base nearly to apex, entire or finely denticulate just below leaf apex; median leaf cells 40–95× 5–10 m m, slightly to strongly incrassate and porose; alar cells not differentiated. Specialized vegetative reproduction unknown. Dioicous. Only male plants seen. Sporophytes unknown.

Distribution and ecology. Orthothecium lapponicum is mostly found at elevations between 700 and 1240 m, with the lowest locality at 460 m. It most commonly grows in close proximity to late snow-beds, on slopes below these on wet soil or rocks, often with trickling meltwater, or sometimes at the margins of small brooklets. For more data see Hedenäs et al. (2019).

Differentiation and variation. Orthothecium lapponicum differs from the most closely related O. sibiricum in the relatively wider, more abruptly tapered and more concave leaves, which are somewhat less abruptly narrowed at their base (see above). It further differs from O. strictum in having mostly larger plants with concave, ovate leaves that are abruptly tapered to a very short acumen, versus moderately concave, ovate-lanceolate leaves that are more gradually tapered to a rather long acumen. Orthothecium chryseon usually has gradually tapered and markedly plicate leaves; it is generally a larger plant than O. lapponicum . Furthermore, the strongly concave leaves of the latter make its shoots tumid and sometimes wider that those of the appressed-leaved O. chryseon . Another good character is found in the mid-leaf cells; these are elongate, with a length to width ratio of 5–10: 1 in O. lapponicum versus linear, and mostly 10–20: 1 in O. chryseon . Orthothecium retroflexum is more similar to O. lapponicum in overall leaf shape, but its leaves are strongly plicate and have hooked leaf apices.