5a. Capsules constricted and strongly plicate at mouth, exostome teeth rudimentary or absent	6
5b. Capsules non-plicate at mouth, exostome teeth well-developed	7
6a. Endostome segments 8, filiform, spores small, unicellular, 14-30 µm wide	O. schofieldii
6b. Endostome segments 16, broad and truncated, spores large multicellular,35-60 µm wide	O. jetteae
7a. Exostome teeth erect to spreading when dry, mostly epilithic species	8
7b. Exostome teeth reflexed or recurved when dry, mostly epiphytic species	13
8a. Laminal cells bistratose, at least in the upper part	9
8b. Laminal cells always unistratose	10
9a. Leaf lamina almost completely bistratose, papillae low and simple	O. hallii
9b. Leaf lamina rather unistratose with numerous bistratose patches, papillae high, clavate or forked	O. pellucidum
10a. Capsules exserted on long setae	O. anomalum
10b. Capsules immersed to emergent, setae short	11
11a. Capsules ovoid to urceolate, 16-ribbed when dry	12
11b. Capsules cylindric, 8-ribbed when dry	O. ibukiense
12a. Vaginula densely hairy with long hairs, exostome teeth roughly papillose	O. urnigerum
12b. Vaginula naked, exostome teeth finely papillose-striated	O. cupulatum
13a. Endostome segments broad, as wide as exostome teeth, united in upper parts and forming a perforated dome	O. callistomum
13b. Endostome segments narrower than exostome teeth, free	14
14a. Leaf margins plane or only slightly recurved near the base	15
14b. Leaf margins recurved or revolute almost throughout	21
15a. Leaves very often keeled	16
15b. Leaves not keeled	17
16a. Leave strongly crisped when dry, usually keeled in the central part	O. crispifolium
16b. Leave undulate and flexuose when dry, usually keeled at the base	O. griffithii
17a. Leaves at least in the apices conspicuous undulate or flexuose when dry	18
17b. Leaves straight or only slightly undulate or flexuose when dry	19
18a. Leaves undulate and flexuose when dry, with rounded-acute apices, endostome segments half of the height of the teeth	O. sinuosum
18b. Leaves flexuose only at the apices when dry, with acute apices, endostome segments almost as tall as teeth	O. consobrinum
19a. Leaves fromovate, somewhat concave bases rather suddenly tapering to the apices	O. notabile
19b. Leaves gradually tapering to the apices	20
20a. Leaves narrowly lanceolate, endostome segments with a smooth outer surface, not united at the base, perichaetial leaves acute	O. subpumilum
20b. Leaves lanceolate, endostome segments remarkably ornamented with vertical striate on the outer surface, sometimes united by broader bases, perichaetial leaves obtuse	O. erubescens
21a. Endostome segments 16	22
21b. Endostome segments 8	29
22a. Vaginula hairy	23
22b. Vaginula naked	24
23a. Endostome segments alternately longer and shorter (the intermediate ones shorter than the primary), calyptra hairy	O. stramineum
23b. Endostome segments of the same length, calyptra naked	O. vermiferum
24a. Endostome segments with lateral appendages	25
24b. Endostome segments without lateral appendages	27
25a. Appendages conspicuously long (the segments resembls a branched tree), often with appendiculae linking contiguous segments	O. moravicum
25b. Appendages short	26
26a. Exostome teeth 8, endostome segments 16, calyptra naked, margins at leaf apex entire	O. revolutum
26b. Exostome teeth 16, endostome segments 16, calyptra sparsely hairy, margins at leaf apex often with a few irregular teeth	O. scanicum
27a. Leaves ovate to ovate-lanceolate, with obtuse apex	O. pamiricum
27b. Leaves oblong-lanceolate to lanceolate, acute to rounded-acute at the apex	28
28a. Endostome formed by 16 well developed narrow segments, calyptra naked	O. pallens
28b. Endostome formed by 8 well developed stout segments and 8 rudimentary ones, calyptra hairy	O. laxum
29a. Vaginula hairy, leaf cells with prominent and commonly forked papillae	O. alpestre
29b. Vaginula naked, leaf cells smooth or with low simple papillae	30
30a. Endostome segments completely erect when dry, slightly striate at base; plants showing dimorphism of branch leaves including ligulate ones with a broadly oval base and margin recurved almost throughout on branches producing archegonia and significantly smaller ones, with margins plane or just a little recurved in the middle part on branches producing antheridia	O. rogeri
30b. Endostome segments incurved when dry, smooth or papillose; no leaf dimorphism present	31
31a. Leaves ligulate to ovate, obtuse to rounded-acute, sometimes partially bistratose	O. crenulatum
31b. Leaves ovate-lanceolate, acute to rounded-acute, always unistratose	32
32a. Capsule ovoid or pyriform when moist, abruptly contracted into seta, segments conspicuous broadly at base, 1/2 to 3/4 as long as the exostome teeth	O. schimperi
32b. Capsule oblong-cylindrical when moist, gradually contracted into seta, segments linear, almost as long as the exostome teeth	O. pumilum