9. Didymodon Hedw.   对齿藓属 dui-chi xian shu

Sp. Musc. Frond. 104. 1801.

 

Plants small to rather robust, usually growing on calcareous soil or rocks, brownish green to reddish brown, in loose or dense tufts. Stems erect, simple or sometimes branched; central strand present, rarely absent. Leaves appressed or contorted when dry, erect-spreading to squarrose-recurved when moist, ovate-lanceolate or broadly lanceolate; margins entire or occasionally crenulate, narrowly revolute; costa strong, percurrent or excurrent, or occasionally ending below the apex, ventral cells of costa narrowly elliptic or rounded quadrate, in cross section with 2 stereid bands; upper leaf cells rounded to rounded quadrate or rhombic, somewhat thick-walled, smooth or bluntly papillose, cell outlines clear; basal cells firm, shortly rectangular to oblong-ovate or rounded quadrate, light green to brownish. Gemmae sometimes present in specialized rhizoids or in leaf axils. Dioicous. Perichaetial leaves similar to stem leaves or slightly differentiated. Setae elongate, erect, reddish brown at the base, yellowish brown at the upper part; capsules erect, oblong-ovoid or cylindrical; annuli not differentiated or in 1–3 rows of cells; opercula shortly rostrate; peristome teeth with a low basal membrane, 16 undivided or split into 32 linear, straight or twisted counterclockwise, densely papillose, occasionally peristome teeth absent. Calyptrae cucullate, smooth, naked. Spores spherical, yellowish green.

 

 

1. Costa slender, ending at or below the leaf apex; leaf cells smooth or unipapillose......................................... 2

1. Costa stout, percurrent or excurent; leaf cells multi-papillose or sometimes unipapillose............................ 3

2. Leaves triangular-lanceolate; costa ending well below the apex; leaf cells smooth; capsules ovoid...........

2. Leaves ovate-lanceolate; costa ending at the apex; leaf cells usually unipapillose; capsules cylindrical....

3. Leaves short and broad, usually broadly ovate to oblong-ovate or ligulate, blunt or rounded at the apex....... 4

3. Leaves narrowly ovate, triangular or linear-lanceolate, gradually acute or acuminate..................................... 7

4. Plants only ca. 0.5 cm high; leaves imbricate, broadly ovate at the base......................... 13. D. perobtusus

4. Plants (1.0–)2.5–6.0 cm high; leaves spreading, narrowly oblong-ovate at the base.................................. 5

5. Plants bright green; leaf apex broad and rounded, slightly cucullate........................................ 18. D. tophaceus

5. Plants reddish brown; leaf apex narrowly and acuminate, not cucullate............................................................. 6

6. Cells of the abaxial surface of costa linear-oblong, walls slightly sinuate; upper leaf cells smooth, or occasionally with 1 indistinct low papilla............................................................................ 10. D. japonicus

6. Cells of the abaxial surface of costa quadrate to short-rectangular, walls not sinuate; upper leaf cells usually with 1 blunt papilla................................................................................................... 11. D. nigrescens

7. Leaves squarrose when moist; leaf cell walls strongly and irregularly thickened............................................. 8

7. Leaves erect-spreading when moist; leaf cell walls not particularly thickened.............................................. 15

8. Leaf bases very broad, deltoid, narrowly lanceolate toward the apex; basal cells linear, very thick-walled, sinuose because of porose walls................................................................................ 9. D. giganteus

8. Leaf bases ovate-lanceolate; basal cells shortly rectangular, slightly thick-walled, not porose................ 9

9. Leaf apices shorter and broader; leaf cells mostly unipapillose, occasionally with 2 papillae..................... 10

9. Leaf apices longer and narrower; leaf cells mostly multipapillose, rarely with 1–2 papillae....................... 11

10. Stems without central strand; leaf margins entire to subentire; leaf cells rounded-oblong to elliptical, almost smooth or papillose with a single, large papilla................................................... 3. D. asperifolius

10. Stems with central strand; leaf margins regularly toothed in the distal 1/2–2/3; leaf cells rounded quadrate to transversely elliptical, with 1–2 papillae.......................................... 6. D. eroso-denticulatus

11. Plants dark green to reddish brown, rather robust, to 8 cm high; leaves strongly squarrose; dorsal surface of costa roughened.................................................................................................................... 8. D. ferrugineus

11. Plants yellowish green, usually less than 4 cm high; leaves slightly squarrose; dorsal surface of costa smooth.............12

12. Leaves triangular-lanceolate; upper leaf margins bistratose.............................................. 14. D. rigidulus

12. Leaves broadly ovate-lanceolate; upper leaf margins unistratose........................................................... 13

13. Basal leaf cells not clearly differentiated, short-rectangular; peristome teeth elongate, twisted counterclockwise three times ........................................................................................................... 7. D. fallax

13. Basal leaf cells distinctly differentiated, narrowly rectangular; if present, peristome teeth short, twisted counterclockwise once...................................................................................................................................... 14

14. Plants 5–8 mm high, in dense tufts; leaves narrowly ovate at the base, not plicate ........12. D. pallidobasis

14. Plants 10–20 mm high, in loose tufts; leaves broadly ovate at the base, plicate.............. 19. D. vinealis

15. Leaf apices cyneous, apically swollen as a propagulum; leaf cells smooth............. 2. D. anserinocapitatus

15. Leaf apices erect or not particularly bent, not swollen; at least upper leaf cells papillose......................... 16

16. Leaves broadly acute at the apex; leaf margins indistinct revolute.................................. 17. D. tectorum

16. Leaves linear at the apex; leaf margins distinctly revolute...................................................................... 17

17. Leaves triangular or deltoid at the base; margins distinctly revolute throughout; leaf cells usually quadrate to hexagonal, regularly arranged, cell walls thinner........................................................................................ 18

17. Leaves broadly ovate-lanceolate to narrowly ovate-lanceolate; margins revolute usually only in the upper part; leaf cells triangular to pentagonal, irregularly arranged, cell walls thicker.......................................... 19