Orthothecium, IN

KEY TO IDENTIFICATION OF THE SPECIES OF ORTHOTHECIUM IN View in CoL NORTHERN EURASIA

(see also Fig. 27 View Fig for synopsis of the most common leaf shape and relative size in the species)

1. Plants small; leaves 0.3–0.5(–0.6) mm wide, not or weakly plicate ....................................................... 2

— Plants large or medium-sized; leaves (0.5–) 0.6–1.2 mm wide, plicate or rarely not plicate ................. 5

2. Leaves rounded at base, more or less abruptly acuminate .......................................... 7. O. sibiricum p.p.

— Leaves slightly narrowed at base, narrowly acute or gradually acuminate ............................................. 3

3. Leaves 0.7–1.2× 0.3–0.4 mm, often distantly arranged, ovate-triangular; leaf margins serrulate, flat or, occasionally, incurved or recurved at places ...... .................................................. 4. O. remotifolium

— Leaves 0.8–1.4(–2.1)×0.2–0.5(–0.6) mm, closely arranged; leaf margins entire or serrulate near apex, narrowly recurved or flat ...................................... 4

4. Leaf margins narrowly recurved; leaves lanceolate or ovate-lanceolate, usually erect, very rarely falcate-secund ............................................... 5. O. strictum View in CoL

— Leaf margins flat; leaves lanceolate or narrow lanceolate, often slightly secund ....... 2. O. intricatum View in CoL

5(1). Leaves oblong-ovate, ovate-lanceolate or broadly ovate, not or weakly plicate .................................. 6

— Leaves ovate-lanceolate to ovate, plicate (only narrow leaves of imperfectly developed morphs are eplicate) .................................................................... 7

6. Shoots moderately densely foliate; leaves homomallous to slightly falcate, ovate-lanceolate to oblong-ovate, slightly to moderately concave, acute or acuminate, not or weakly plicate; leaf margins flat; plants olivaceous or yellowish-green, often with brownish tint, occasionally dark brown .... 3. O. brunnescens

— Shoots densely foliate, terete; leaves ovate to broadly ovate, strongly concave, abruptly apiculate, not plicate; leaf margins narrowly recurved; living plants often red, plants in herbarium collections yellowgreen or golden-yellow ............... 6. O. lapponicum View in CoL

7. Leaves weakly plicate, rounded at base .................. ................................................. 7. O. sibiricum p.p.

— Leaves strongly plicate, slightly narrowed at base 8

8. Plants purple-reddish; leaves erect all along the stem, straight or, occasionally, homomallous, lanceolate, moderately to longly tapered, not especially concave; leaf margin recurved nearly to the base, except the small part in leaf corners, where leaf is abruptly rounded; decurrencies absent or inconspicuous; laminal cells 50–150 µm long .............. 1. O. rufescens View in CoL

— Plants golden-green, bronze to deeply vinaceous red; stems terete-foliate; leaves straight, with distal parts appressed or erect, ovate to lanceolate, moderately to longly tapered or abruptly apiculate and with reflexed apiculus; leaf margin recurved to the base extending to short decurrency, only slightly rounded to base; laminal cells 50–85 µm long ...................... 8

9. Leaves ovate-lanceolate to lanceolate, ending in short, straight, flexuose, occasionally incurved or recurved apiculus ............................ 7. O. chryseon

— Leaves ovate to broadly oblong-ovate, ending in strongly revolute apiculus .......... 8. O. retroflexum