1. Margins at leaf shoulders regularly dentate, serrate, or ciliate on at least some leaves.................................. 2.
1. Margins at leaf shoulders mostly entire but occasionally and irregularly with 1 to several small teeth...... 11
2. Leaves lacking border of hyaline cells........................................................3
2. Leaves bordered distally with elongate hyaline cells..................................5
3. Leaf shoulders ciliate.................................................... 1. S. armatispinosus
3. Leaf shoulders only dentate-serrate.....................................................4
4. Rhizoids dark-red; distal cells of cancellinae sharply demarcated from adjacent green cells of upper laminae, and cancellinae thus distinct; cells of upper laminae pluripapillose abaxially and adaxially .................... 5. S. gardneri
4. Rhizoids brown; distal cells of cancellinae gradually blending with adjacent green cells of upper laminae and cancellinae thus indistinct; cells of upper laminae smooth abaxially, bulging-mammillose adaxially.....................................................9. S. japonicus
5. Cells of upper laminae smooth or unipapillose abaxially.................................6
5. Cells of upper laminae pluripapillose abaxially...............................................8
6. Cells of upper laminae mostly smooth or minutely papillose but some cells abaxially spinose in intramarginal rows (best seen in cross section)...........................7
6. Cells of upper laminae clearly unipapillose; intramarginal rows of abaxially spinose cells lacking..............................................................................2. S. armatus
7. Costa on most leaves remotely spinose adaxially; cilia on leaf shoulders mostly 30–60 µm long ........................................3. S. chenii
7. Costa on most leaves abundantly spinose adaxially; cilia on leaf shoulders mostly 70–90 µm long ....................................................................7. S. hongkongensis
8. Leaves with large, forward-pointing peg-like papillae distally on abaxial surface; costa papillose-spinose abaxially..........................................................15. S. spiculosus
8. Leaves lacking large peg-like papillae distally on dorsal surface; costa smooth abaxially........................ 9
9. Leaf bases narrow, scarcely wider than upper laminae; cells of upper laminae pellucid; leaf shoulders with small delicate teeth...................................17. S. trachyphyllus
9. Leaf bases broader than upper laminae; cells of upper laminae obscure; leaf shoulders with large, often spreading-recurved teeth or cilia...........................10
10. Leaves erect and only slightly contorted when dry; upper laminae straight when wet, several times longer than lower laminae....................................6. S. hainanensis
10. Leaves tightly curled-contorted when dry; upper laminae usually falcate when wet, only to ca. twice as long as lower laminae.....................................11. S. orientalis
11. Upper laminae very short, ½ or less length of lower laminae.........8. S. involutus
11. Upper laminae much longer than lower laminae..................................12
12. Leaves erect and straight when dry......................................10. S. muelleri
12. Leaves variously contorted when dry...............................................13
13. Stems elongate, often more or less repent and with erect ascending branches; leaves flexed, with prominent shoulders; upper laminae tubulose wet and dry; plants and leaf bases often red-brown or golden..................................4. S. flammeonervis
13. Stems short and erect, or plants with stemless appearance; leaves neither flexed nor with prominent shoulders; upper laminae plane to canaliculate when moist but not tubulose; plants green ......................... 14
14. Cells of upper laminae smooth or unipapillose abaxially; gemmae filamentous, borne adaxially at midleaf...................................................12. S. parasiticus
14. Cells of upper laminae pluripapillose abaxially; gemmae various.............15
15. Distal abaxial cells of upper laminae with large distally-pointing peg-like multifid papillae................. 15. S. spiculosus
15. Distal abaxial cells of upper laminae lacking peg-like papillae.................. 16
16. Gemmae borne adaxially at midleaf or lower..........................................17
16. Gemmae borne adaxially only on leaf tip................................................ 18
17. Gemmae filamentous, borne at midleaf, cancellinae acute distally......................................... 14. S. semiliber
17. Gemmae short, often curved, usually borne at base of upper laminae just distal to cancellinae; cancellinae rounded distally...........................16. S. tjibodensis
18. Leaves oblong, 1–2 mm long......................................17. S. trachyphyllus
18. Leaves linear to acuminate, 2–5 mm long....................................... 19
19. Cells of upper laminae obscure, pluripapillose with small low papillae; leaf shoulders lacking teeth............................................13a. S. prolifer var. prolifer
19. Cells of upper laminae pellucid, with bulging multifid papillae; leaves acuminate; leaf shoulders occasionally bearing small (rarely large and cilia-like) sharp teeth................ ........................................13b. S. prolifer var. tosaensis