1. Leaves obovate-spathulate; costae excurrent; leaf cells irregularly rectangular, twice as long as width; capsules longitudinally striate when dry..........................................6. R. parvulum
1. Leaves elliptical, broadly obovate or orbicular; costae ending below the apex or percurrent; leaf cells isodiametric, hexagonal or rounded; capsules not striate when dry................................2
2. Leaves long-elliptical or long-obovate; costae percurrent or ending just below the apex................3
2. Leaves broadly obovate or rounded; costae ending well below the apex.....................................4
3. Leaves long-elliptical; leaf cells 30–50 μm × 40–80 µm, irregularly rounded-oblong, cell walls thickened at corners.................................................................................9. R. striatulum
3. Leaves long-obovate; leaf cells 55–90 μm × 95–135 µm, regularly hexagonal, cell walls usually uniformly thickened.............................................................................10. R. tuomikoskii
4. Leaves elliptical or obovate, plane, not crisped when dry; leaf apices apiculate....................5
4. Leaves broadly elliptical, broadly obovate or orbicular, crisped when dry; leaf apices rounded.................. 7
5. Leaves often crowded at apex, squarrose; walls of marginal cells irregularly thickened and distinctly porose
......................................................................................3. R. horikawae
5. Leaves scattered, spreading; walls of marginal cells not porose...................................6
6. Leaf margins bordered by 1–2 rows of rectangular cells; leaf base not decurrent... 7. R. pseudopunctatum
6. Leaf margins bordered by 2–4 rows of elongate cells; leaf base long-decurrent................. 8. R. punctatum
7. Leaves large, broadly elliptical, undulate; cell walls strongly porose......................4. R. magnifolium
7. Leaves small, nearly rounded, scarcely undulate; cell walls scarcely or weakly porose..................8
8. Leaves scattered at stem apex; margins bordered by 1–2 rows of more or less rectangular cells.......... 2. R. hattorii
8. Leaves often dense at stem apex; margins bordered by 3–4 rows of narrowly elongated cells.................... 9
9. Leaves dark green, marginal cells rectangular, not or scarcely porose...........................1. R. gracile
9. Leaves pale green, marginal cells irregularly elongate, weakly to distinctly porose.........5. R. nudum