The genus Physcomitrium consists of some 68 species in the world, with 22 species better understood (Crosby et al. 2000). Eight species are recognized in China.
1. Leaves narrowly ligulate-lanceolate or oblong-lanceolate; margins serrate nearly throughout.................. 1. P. coorgense
1. Leaves oblong-obovate to obovate; margins entire or crenate to bluntly denticulate in the upper part........... 2
2. Leaf margins scarcely bordered with slightly elongate cells; capsules spherical, with a very short, indistinct neck..............................................8. P. sphaericum
2. Leaf margins more distinctly bordered by elongate cells; capsules short-pyriform or cup-shaped, with a distinct neck...........................................................3
3. Leaf margins almost entire throughout.........................................................................................4
3. Leaf margins crenate or bluntly denticulate in the upper part.............................................................................. 5
4. Plants small, 2–5 mm high; costa yellowish, percurrent; opercula conic with a small, rounded apiculus ...............................................................3. P. eurystomum
4. Plants larger, 8–14 mm high; costa green, shortly excurrent; opercula conic with a beak-like or more distinct apiculus...............................2. P. courtoisii
5. Leaves oblong-obovate, acute at apex; margins bordered by 2–3 rows of yellowish cells; capsules spherical, with an indistinct apophysis.............4. P. japonicum
5. Leaves ovate-lanceolate to oblong-lanceolate, acuminate at apex; margins bordered by 1–2 rows of greenish cells; capsules shortly pyriform, with a distinct apophysis................................................................... 6
6. Plants rather small, 3–5 mm high; leaf cells hexagonal to rounded short-rectangular.......... 6. P. repandum
6. Plants larger, 8–15 mm high; upper and median leaf cells oblong-hexagonal to short-rectangular, lower cells elongate-rectangular..........................................7
7. Alar cells distinctly enlarged to slightly inflated; setae 6–14 mm long.... 5. P. pyriforme
7. Alar cells not differentiated from other basal cells; setae 2–4 mm long.................. 7. P. sinensi-sphaericum