1	Sterile leaves monomorphic, spirally arranged, linear or linear-lanceolate, with long white apical seta		(2)
+	Sterile leaves dimorphic, arranged in 4 ranks, 2 dorsal and 2 ventral leaves, rarely nearly monomorphic, without long white apical seta		(4)
2 (1)	Leaves thickly leathery, obtuse at apex.		1 S. sibirica
+	Leaves thinly leathery, acuminate at apex		(3)
3 (2)	Apical seta ca. 1/3 as long as leaves.		2 S. vardei
+	Apical seta ca. 1/5 as long as leaves.		3 S. indica
4 (1)	Stems and branches cylindrical, often reddish; sterile leaves nearly monomorphic, adpressed to stems and branches		(5)
+	Branches often compressed; leaves dimorphic, dorsal leaves ascending, ventral leaves spreading		(6)
5 (4)	Leaves not white-margined.		4 S. sanguinolenta
+	Leaves distinctly white-margined.		5 S. albocincta
6 (4)	Strobili lax, not distinct from sterile stems; sporophylls monomorphic or dimorphic, almost conform with sterile leaves at same rank (non-resupinate) (see also 42b)		(7)
+	Strobili compact, distinct from sterile stems; sporophylls in 4 ranks, monomorphic or dimorphic (dorsal sporophylls larger than ventral ones, rarely smaller)		(9)
7 (6)	Strobili cylindrical; sporophylls monomorphic, smaller than ventral leaves.		6 S. helvetica
+	Strobili rather loosely dorsiventrally compressed; sporophylls dimorphic, nearly conform with sterile leaves at same rank		(8)
8 (7)	Leaves denticulate at margin.		7 S. nipponica
+	Leaves shortly ciliolate at margin.		8 S. pseudonipponica
9 (6)	Strobili tetragonal; sporophylls nearly monomorphic		(10)
+	Strobili dorsiventrally complanate; dorsal and ventral sporophylls dimorphic		(41)
10 (9)	Stems forming rosettes, curling inward when dry		(11)
+	Stems not forming rosettes, not curling inward when dry		(12)
11 (10)	Dorsal and ventral leaves denticulate at margin.		9 S. tamariscina
+	Dorsal leaves reflexed at margin; acroscopic margin of ventral leaves brown, membranous, lacerate.		10 S. pulvinata
12 (10)	Main stems creeping or prostrate in basal portion to scandent; rhizophores borne throughout stems		(13)
+	Main stems erect, suberect, or ascending with short prostrate basal portion; rhizophores usually borne on basal to middle portions of main stem		(24)
13 (12)	Main stems scandent, up to 1-2 m or longer		(14)
+	Main stems creeping, decumbent, or scandent, usually less than 1 m		(15)
14 (13)	Axillary and ventral leaves with large basal auricles; dorsal leaves slightly white-margined; sporophylls ovate, acute or cuspidate; base of rhizophores without spines.		11 S. willdenowii
+	Axillary and ventral leaves with small basal auricles; dorsal leaves white-margined; sporophylls ovate-lanceolate, acuminate; base of rhizophores with a few spines.		12 S. helferi
15 (13)	Plants xerophytic, curling when dry; leaves ciliolate at margin		(16)
+	Plants not xerophytic, not curling when dry; leaves entire or denticulate at margin		(18)
16 (15)	Dorsal leaves slightly smaller than and overlapping ventral leaves; leaves slightly lacerate and densely long ciliolate at margin.		13 S. nummularifolia
+	Dorsal leaves much smaller than and not largely overlapping ventral leaves		(17)
17 (16)	Stems and branches scarlet; ventral leaves reflexed; margin of leaves sparsely toothed and long ciliolate at acroscopic base, entire elsewhere.		14 S. rossii
+	Stems and branches stramineous; ventral leaves not reflexed; margin of leaves shortly ciliolate throughout.		15 S. sinensis
18 (15)	Leaves entire		(19)
+	Leaves denticulate or ciliolate at margin		(21)
19 (18)	Dorsal leaves auriculate at basiscopic base.		16 S. limbata
+	Dorsal leaves not auriculate		(20)
20 (19)	Sporophylls not carinate on abaxial surface.		17 S. uncinata
+	Sporophylls carinate on abaxial surface.		18 S. hainanensis
21 (18)	Stems not articulate; rhizophores borne on ventral side in axils of branches		(22)
+	Stems slightly articulate beneath branching; rhizophores borne on dorsal side in axils of branches		(23)
22 (21)	Leaves not white-margined, leaves on main stems and lateral branches ciliolate at margin, those on ultimate branches often subentire.		19 S. siamensis
+	Leaves white-margined, denticulate or shortly ciliolate.		20 S. davidii
23 (21)	Stems with a single vascular bundle.		21 S. remotifolia
+	Stems with 3 vascular bundles.		22 S. kraussiana
24 (12)	Rhizophores borne on basal and middle portions of main stem or sometimes also on upper portion; leaves on main stem dimorphic		(25)
+	Rhizophores restricted to basal or lower portion of main stem or to prostrate rhizome; leaves on main stem monomorphic		(32)
25 (24)	Plants erect; lateral branches regularly pinnately branched, twice forked, or simple; leaves entire or minutely denticulate at apex		(26)
+	Plants erect, suberect, or ascending with prostrate rhizome; lateral branches many times pinnately branched; leaves denticulate		(28)
26 (25)	Main stems 3-5 mm in diam., apical part black when dry; stomata invisible on dorsal leaves.		23 S. picta
+	Main stems 2-3 mm in diam., apical part not black when dry; stomata on adaxial surface of dorsal leaves visible		(27)
27 (26)	Lateral branchlets simple or forked, or basal branchlets often forked; dorsal leaves overlapping distally.		24 S. delicatula
+	Lateral branchlets simple, sometimes with irregular longer branches; dorsal leaves parallel, not overlapping distally.		25 S. wallichii
28 (25)	Leaves subleathery, shiny when dry; dorsal leaves aristate, arista ca. 1/2 as long as leaves or longer.		26 S. commutata
+	Leaves herbaceous, not shiny when dry; dorsal leaves acuminate to aristate, arista very short		(29)
29 (28)	Ventral leaves 4.5-7 mm.		27 S. rolandi-principis
+	Ventral leaves less than 4.5 mm		(30)
30 (29)	Ventral leaves ovate-triangular or ovate-lanceolate; dorsal leaves aristate; surface of dorsal and ventral leaves scabrous.		28 S. scabrifolia
+	Ventral leaves ovate-oblong or oblong-falcate; dorsal leaves acuminate or very shortly aristate; surface of leaves glabrous or that of ventral leaves scabrous		(31)
31 (30)	Dorsal and ventral leaves glabrous.		29 S. doederleinii
+	Ventral leaves scabrous.		30 S. trachyphylla
32 (24)	Stems and branches pubescent		(33)
+	Stems and branches glabrous		(37)
33 (32)	Main stems isotomously branched.		31 S. pubescens
+	Main stems pinnately branched		(34)
34 (33)	Plants 45-100 cm high or more; axillary leaves biauriculate at base, ventral leaves auriculate at acroscopic base		(35)
+	Plants 10-45 cm high; axillary leaves not auriculate at base		(36)
35 (34)	Leaf portion of main stems and branches pubescent on both sides; main stems zigzag; leaves white-margined.		32 S. trichoclada
+	Leaf portion of main stems glabrous, ventral side of branches pubescent; main stems not zigzag; leaves not white-margined.		33 S. pseudopaleifera
36 (34)	Leaves thick, shrunken when dry; leaves on main stems peltate.		34 S. braunii
+	Leaves thin, not shrunken; leaves on main stems basifixed.		35 S. biformis
37 (32)	Plants usually more than 50 cm high, main stems robust, up to 4-5 mm in diam.; branches including leaves 5-10 mm wide.		36 S. superba
+	Plants usually less than 50 cm high, main stems 1-2 mm in diam., not so robust; branches including leaves less than 5 mm wide		(38)
38 (37)	Leaves on main stems approximate		(39)
+	Leaves on main stems distant		(40)
39 (38)	Main stems reddish.		37 S. stauntoniana
+	Main stems stramineous.		38 S. involvens
40 (38)	Leaves on main stems peltate at base, not white-margined, ciliolate, very shrunken when dry.		39 S. mairei
+	Leaves on main stems basifixed, white-margined, denticulate, not shrunken when dry.		40 S. moellendorffii
41 (9)	Strobili non-resupinate, i.e., dorsal sporophylls smaller than ventral ones		(42)
+	Strobili resupinate, i.e., dorsal sporophylls larger than ventral ones		(46)
42 (41)	Strobili rather lax, often forked (see also 6a)		(43)
+	Strobili shortly compact, solitary (or sometimes forked in S. prostrata)		(44)
43 (42)	Fertile branches short, pinnately branched; leaves up to 3.2 ?1.8 mm, margin denticulate, shortly ciliolate at base.		41 S. pallidissima
+	Fertile branches erect or ascending, forked; leaves up to 2.3 ?1.2 mm, shortly ciliolate at margin, ciliolate at base.		42 S. laxistrobila
44 (42)	Leaves denticulate at margin.		43 S. tama-montana
+	Leaves long ciliolate at margin		(45)
45 (44)	Strobili less than 4 mm; sporophylls plane.		44 S. prostrata
+	Strobili usually over 8 mm, up to 25 mm; larger ventral sporophylls navicular.		45 S. longistrobilina
46 (41)	Main stems erect or suberect; rhizophores restricted to basal or lower portion of main stems		(47)
+	Main stems prostrate or at least lower part prostrate, branches creeping or erect; rhizophores at intermittent intervals		(55)
47 (46)	Plants more than 30 cm high		(48)
+	Plants usually less than 30 cm high		(49)
48 (47)	Plants erect, 40-75 cm high; rhizophores restricted to basal portion of main stems.		46 S. decipiens
+	Plants suberect, 30-40 cm high; rhizophores present in lower part of main stems.		47 S. bodinieri
49 (47)	Sporophylls strongly dimorphic, ventral sporophylls up to 1/2 as long as dorsal ones		(50)
+	Sporophylls not strongly dimorphic, ventral sporophylls ca. 2/3 as long as dorsal ones		(52)
50 (49)	Plants up to 30 cm high; main stems robust; dorsal leaves obovate-aristate.		48 S. pennata
+	Plants 5-15(-25) cm high; main stems thin		(51)
51 (50)	Ventral leaves up to 3 mm; sporophylls minutely denticulate.		49 S. leptophylla
+	Ventral leaves up to 3 mm; sporophylls sparsely ciliate.		50 S. minutifolia
52 (49)	Main stems tuberous at base.		51 S. chrysocaulos
+	Main stems not tuberous at base		(53)
53 (52)	Axillary leaves ovate-deltoid.		52 S. effusa
+	Axillary leaves ovate-lanceolate		(54)
54 (53)	Plants erect, main stems simple, branched in upper portion; leaves on stems and branches rather distant; rhizophores restricted to basal portion of main stems; base of ventral leaves shortly ciliolate.		53 S. labordei
+	Plants ascending to erect, main stems branched in lower and upper portions; leaves on main stems rather approximate; rhizophores on lower portion of main stems; base of ventral leaves long ciliolate.		54 S. repanda
55 (46)	Stems long creeping, fertile branches not erect, plants up to 30 cm or more; rhizophores on main stems and branches at intermittent intervals		(56)
+	Main stems and branches prostrate or fertile branches suberect, plants usually less than 20 cm, or main stems erect, normally less than 25 cm high; rhizophores on prostrate stems or restricted to basal portion of erect main stems		(61)
56 (55)	Dorsal leaves obovate, long ciliolate in upper portion.		55 S. bisulcata
+	Dorsal leaves not as above		(57)
57 (56)	Ultimate branches including leaves 10-15 mm wide.		56 S. megaphylla
+	Ultimate branches including leaves less than 8 mm wide		(58)
58 (57)	Dorsal leaves long aristate; sporophyll-pteryx of dorsal sporophylls not reaching apex (incomplete)		(59)
+	Dorsal leaves acuminate or shortly aristate; sporophyll-pteryx of dorsal sporophylls reaching apex or almost so (complete)		(60)
59 (58)	Basiscopic margin of ventral leaves entire.		57 S. ornata
+	Basiscopic margin of ventral leaves ciliolate.		58 S. amblyphylla
60 (58)	Leaves glabrous.		59 S. monospora
+	Leaves scabrous.		60 S. trichophylla
61 (55)	Prostrate stems very short, thin; plants small; fertile stems prominent		(62)
+	Plants not as above		(63)
62 (61)	Sporangia only on ventral side of strobilus; sporophylls denticulate.		61 S. devolii
+	Sporangia on both sides of strobilus; sporophylls long ciliolate.		62 S. ciliaris
63 (61)	Acroscopic base of ventral leaves not long ciliolate; leaves denticulate or shortly ciliolate at margin		(64)
+	Acroscopic base of ventral leaves long ciliolate		(68)
64 (63)	Dorsal leaves rounded or obtuse at apex; leaves denticulate at margin.		63 S. kouytcheensis
+	Dorsal leaves acuminate or aristate; leaves denticulate or shortly ciliolate at margin		(65)
65 (64)	Fertile branches short, complanate with sterile main stems and branches, creeping or ascending		(66)
+	Fertile branches long, erect		(67)
66 (65)	Leaves shortly ciliolate at margin.		64 S. boninensis
+	Leaves minutely denticulate at margin.		65 S. heterostachys
67 (65)	Dorsal leaves cordate at base, margin shortly ciliolate.		53 S. labordei
+	Dorsal leaves not cordate at base, margin minutely denticulate.		65 S. heterostachys
68 (63)	Fertile branches erect; ventral leaves involute in dry conditions		(69)
+	Fertile branches creeping; ventral leaves not involute in dry conditions		(71)
69 (68)	Basiscopic base of ventral leaves with few long cilia.		66 S. kurzii
+	Basiscopic base of ventral leaves shortly ciliolate, elsewhere subentire		(70)
70 (69)	Sporophylls obviously dimorphic.		67 S. xipholepis
+	Sporophylls slightly dimorphic.		68 S. vaginata
71 (68)	Ventral leaves oblong-falcate; dorsal leaves ovate-lanceolate.		69 S. drepanophylla
+	Ventral leaves not oblong-falcate; dorsal leaves ovate or suborbicular		(72)
72 (71)	Leaves not white-margined, sparsely ciliolate.		70 S. chaetoloma
+	Leaves distinctly white-margined		(73)
73 (72)	Ventral leaves denticulate at margin, bearing several long hairs at basal portion.		71 S. lutchuensis
+	Ventral leaves long ciliolate at margin.		72 S. albociliata