1	"Free-floating, aquatic plants"	2
1	"Anchored plants, usually terrestrial, epiphytic or lithophytic"	4
2	"Sterile lamina 1–3-pinnate, 40–400 mm long, 10–200 mm wide"	"Parkeriaceae {Ceratopteris thalictroides}"
2	"Sterile lamina simple, paired and 7–30 (–40) mm long, or crowded and 1–2 mm long"	3
3	"Frond of 2 floating, foliar leaves and 1 submerged, root-like, sporocarp-bearing leaf; floating leaves broad or rounded"	"Salviniaceae {Salvinia molesta}"
3	"Frond of numerous, crowded, ovate to triangular, bilobed leaves; spore capsules in axil of submerged leaf lobe"	"Azollaceae {Azolla}"
4	"Stems jointed, rush-like, sometimes hollow; leaves small, whorled, joined in a sheath at stem nodes"	"Equisetaceae {Equisetum arvense}"
4	"Stems not jointed; leaves not whorled and joined in a sheath at stem nodes"	5
5	"Sporangia in the axil of a forked leaf and fused in groups of 2 or 3, or in the axils of sporophylls (often in cone-like structures), or in swollen leaf bases"	6
5	"Sporangia free, laminal or marginal and either scattered or in clusters (which may in turn be confluent), or sporangia occurring in scattered or clustered sori, aggregated into a spike or enclosed in sessile or stalked receptacles"	9
6	"Sporangia fused in groups of 2 or 3 and borne in axil of forked leaf"	Psilotaceae
6	"Sporangia solitary, in the axils of sporophylls (often in cone-like structures) or in swollen leaf bases"	7
7	"Sporangia in swollen leaf bases on adaxial side; plants aquatic or semi-aquatic"	"Isoetaceae {Isoetes}"
7	"Sporangia in the axils of sporophylls that are often aggregated in cone-like structures"	8
8	"Sterile leaves and sporophylls with a minute basal ligule; sporangia dimorphic; megasporangia assuming the shape of the 4 developing megaspores; microsporangia globose to reniform"	"Selaginellaceae {Selaginella}"
8	"Sterile leaves and sporophylls lacking a basal ligule; sporangia uniform, subglobose to reniform"	Lycopodiaceae
9	"Fronds comprising a sterile lamina and a fertile spike diverging from a common basal stalk"	Ophioglossaceae
9	"Sterile and fertile fronds borne separately on the rhizome, or all mature fronds fertile"	10
10	"Sori completely enclosed in sessile or stalked woody spore receptacles at the base of the stipe; sterile fronds with 2 or 4 apical leaflets in opposite pairs, or leafless and consisting of a stipe only"	Marsileaceae
10	"Sori not enclosed in spore receptacles, either completely exposed or partially protected by an indusium or a reflexed leaf margin; sterile fronds simple or variously dissected, lacking apical leaflets"	11
11	"Pinnae with swollen, jointed bases; sori composed of a double row or ring of free sporangia, or fused in a bivalved synangium"	Marattiaceae
11	"Pinnae lacking swollen, jointed bases; sori scattered or aggregated but not composed of a double row or ring of free sporangia, or fused in a bivalved synangium"	12
12	"High-climbing plants; fertile and sterile pinnules markedly different; sori borne on marginal projections of pinnules"	"Lygodiaceae {Lygodium}"
12	"Plants not climbing or, if climbing, sori borne on the margin or underside of lamina, not on apices of laminal axes nor on marginal projections"	13
13	"Sori on short pinnate or digitate fertile segments at apices of stipe-like, often dichotomously branching lamina axes"	Schizaeaceae
13	"Sori borne on the margin or underside of lamina, not on pinnate or digitate fertile segments at the apices of lamina axes"	14
14	"Rhizome and stipe spongy; sporangia solitary, in 2 marginal rows; aquatic and semi-aquatic ferns"	Ceratopteris
14	"Rhizome and stipe not spongy; sporangia not solitary in marginal rows; mostly terrestrial, lithophytic or epiphytic ferns"	15
15	"Rhizome a single arborescent trunk over c. 2 m tall; tree ferns"	16
15	"Rhizome not an arborescent trunk"	18
16	"Sporangia massed along minor veinlets of lower pinnules of primary pinnae, becoming confluent, not aggregated in discrete sori, exindusiate"	Todea
16	"Sori discrete, with a hood-shaped or 2-lipped indusium, or exindusiate but with a basal ring of scales"	17
17	"Stipe bases scaly, lacking hairs; sori between midrib and margin, with a hood-shaped indusium, or exindusiate but with a basal ring of scales"	"Cyatheaceae {Cyathea}"
17	"Stipe bases hairy, lacking scales; sori marginal, with a 2-lipped indusium"	"Dicksoniaceae {Dicksonia}"
18	"Fronds appearing dichotomously branched, or rarely in opposite pairs (Diplopterygium ), usually with dormant buds in the axils"	Gleicheniaceae
18	"Fronds simple or variously divided, not appearing dichotomously branched, without dormant buds in the axils"	19
19	"Ultimate segments small and rounded with strongly reflexed margins forming pouch-like cavities"	20
19	"Ultimate segments variable, lacking strongly reflexed margins that form a pouch-like cavity"	21
20	"Lamina filiform or pinnate; rhizome thick, densely clothed in reddish hairs"	"Platyzomataceae {Platyzoma microphyllum}"
20	"Lamina of 2 pinnate branches at the stipe apex; rhizome slender and wiry with scattered, appressed scales"	"Gleichenia abscida"
21	"Sporangia in discrete, oblong or irregular patches, restricted to the basal half of minor costules; fronds filmy"	Leptopteris
21	"Sporangia not as above"	22
22	"Sori covered by an indusium or by a reflexed pinna/pinnule margin"	23
22	"Sori lacking an indusium or other form of covering"	47
23	"Most or all sori borne on the underside of the pinnae/pinnules away from the margins"	24
23	"Sori confined to marginal or submarginal areas of ultimate lamina segments; if submarginal usually covered by a reflexed pinna/pinnule margin"	32
24	"Sori rounded or elliptic"	25
24	"Sori elongate"	29
25	"Lamina simple, 1-pinnate or 1-pinnate-pinnatifid"	26
25	"Lamina 2–4-pinnate or pinnatifid"	28
26	"Sori on anastomosing veins parallel and usually adjacent to midrib; indusium semi-circular"	Doodia
26	"Sori on free veins, on free included veinlets or at vein tips; usually not adjacent to midrib; indusium orbicular to reniform"	27
27	"Pinnae articulated to the rachis, or stipe articulated to a phyllopodium; rhizome scales peltately attached; hydathodes prominent on upper surface of lamina at vein endings; basal veins from adjacent costules not uniting to form a translucent sinus membrane between 2 pinna lobes"	Davalliaceae
27	"Pinnae not articulated to the rachis; stipe not articulated to a phyllopodium; rhizome scales attached along their basal margins; hydathodes absent; basal veins from adjacent costules often uniting and terminating in a translucent sinus membrane between 2 pinna lobes"	Thelypteridaceae
28	"Basal pinnae often enlarged on their basal side; indusium usually glabrous, or with long silky hairs; rhizome scales ±glabrous"	Dryopteridaceae
28	"Basal pinnae not enlarged on their basal side; indusium with short capitate hairs; rhizome scales hairy"	Macrothelypteris
29	"Sori in long grooves close to midrib or following anastomosing veins; groove margins extending into flaps; lamina simple; rhizome with clathrate scales"	Vittariaceae
29	"Sori not in grooves, covered by an indusium; lamina usually 1–4-pinnate; rhizome scales usually not clathrate (except Aspleniaceae)"	30
30	"Sori parallel to midrib of ultimate segments"	Blechnaceae
30	"Sori oblique to midrib of ultimate segments"	31
31	"Rhizome scales clathrate"	Aspleniaceae
31	"Rhizome scales not clathrate"	Athyriaceae
32	"Indusium bivalved or cup-shaped"	33
32	"Indusium ±rounded to elongate, flap-like or a reflexed pinna/pinnule margin"	36
33	"Sori borne on short or elongate receptacles terminating the veins or projecting from the lamina margin; lamina filmy, 1 cell thick (rarely 2 or 3 cells) and translucent, or lamina reduced to minute hairs (Sphaerocionium ) or a barely perceptible wing along axes of frond (Crepidomanes p.p. , Cephalomanes )"	Hymenophyllaceae
33	"Sori not borne on receptacles; lamina not as above"	34
34	"Rhizome and stipe base scaly, lacking hairs"	Davalliaceae
34	"Rhizome and stipe base hairy, lacking scales"	35
35	"Indusium of 2 distinct lips; inner lip membranous; outer lip a reflexed pinnule lobe"	"Culcitaceae {Calochlaena}"
35	"Indusium cup-like"	Dennstaedtia
36	"Sori rounded to elliptic"	37
36	"Sori elongate or confluent along pinna margin"	42
37	"Indusium false (a reflexed pinna margin) or a flap opening towards centre or base of pinna"	38
37	"Indusium reniform, semicircular, half-cup-shaped or a broadly attached flap opening towards pinna margin"	40
38	"Rhizome and stipe base hairy, lacking scales"	Hypolepis
38	"Rhizome and stipe base scaly, lacking hairs"	39
39	"Each ultimate segment with a single vein; fronds to c. 6 cm tall; epiphytic ferns"	Calymodon
39	"Each ultimate segment with many veins; most fronds at least 10 cm tall; terrestrial ferns"	Adiantaceae
40	"Rachis deeply grooved; lower margins of pinnae and pinnules decurrent on edge of rachis groove; midrib rarely present"	Lindsaeaceae
40	"Rachis not deeply grooved; lower margins of pinnae and pinnules not decurrent; midrib usually present"	41
41	"Rhizome and stipe base hairy, lacking scales"	Microlepia
41	"Rhizome and stipe base densely scaly, lacking hairs"	Oenotrichia
42	"Lamina simple, entire; sori in long grooves with groove margins extending inwards as indusium-like flaps; rhizome scales clathrate; usually epiphytic ferns"	Vittaria
42	"Lamina 1–4-pinnate or pinnate-pinnatifid; sori not in grooves; rhizome scales not clathrate; usually terrestrial ferns"	43
43	"Sori covered by a reflexed pinnule margin, sometimes also by a membranous true indusium (best seen in immature fronds)"	44
43	"Sori covered only by a true indusium attached at the base and opening towards the margin"	46
44	"Frond to 2 (–3) m tall; rhizome long-creeping, hairy or scaly; stipe and rachises predominantly yellow-brown"	Dennstaedtiaceae
44	"Frond to 50 (–70) cm tall, with a creeping to erect, scaly rhizome and dark brown to black rachises, or frond to 2 m tall, but with a short, erect rhizome and predominantly pale stipe and rachises"	45
45	"Stipe and rachises dark brown to black, usually glossy; fronds to 50 (–70) cm tall"	Adiantaceae
45	"Stipe and rachises pale green, stramineous, pale brown or mid-brown, rarely glossy; fronds usually more than 70 cm tall"	Pteridaceae
46	"Lower margins of pinnae and pinnules decurrent on edge of rachis groove; midrib rarely present"	Lindsaeaceae
46	"Lower margins of pinnae not decurrent on edge of rachis groove; midrib usually present"	"Nephrolepis acutifolia"
47	"Sori discrete or confluent but not covering all of the underside of fertile pinnae/pinnules"	48
47	"Sori/sporangia covering the whole of the underside of fertile pinnae/pinnules"	60
48	"Sori rounded or elliptic, remaining discrete"	49
48	"Sori elongate or, if rounded, submarginal and confluent"	55
49	"Lamina of 2 large, flabellate and deeply incised halves; rhizome with coarse, dark bristles"	Dipteridaceae
49	"Lamina simple to many times pinnate, not of 2 large, flabellate and deeply incised halves; rhizome usually with scales or hairs"	50
50	"Lamina 2–5-pinnate; terrestrial ferns"	51
50	"Lamina simple, 1-pinnatifid, 1-pinnate, 1-pinnate-pinnatifid or dichotomously branched; mostly epiphytic ferns"	52
51	"Rhizome scaly"	Dryopteridaceae
51	"Rhizome hairy, without scales"	Hypolepis
52	"Sori forming 2 irregular rows between each pair of primary veins"	Coveniella
52	"Sori not forming 2 irregular rows between each pair of primary veins"	53
53	"Rhizome scales peltate and/or clathrate; stipes articulated to the rhizome or to a short, erect phyllopodium (not articulated in Drynaria )"	Polypodiaceae
53	"Rhizome scales neither peltate nor clathrate; usually attached along their basal margins; stipes not articulated to the rhizome nor to a short, erect phyllopodium (not articulated in Drynaria )"	54
54	"Lamina simple,1-pinnatifid, 1-pinnate, or dichotomously branched; veins free, simple or forked"	Grammitidaceae
54	"Lamina 1-pinnate-pinnatifid; veins nearest the costa usually anastomosing with an excurrent vein"	Pneumatopteris
55	"Sporangia borne on narrow, apical portion of lamina"	Belvisia
55	"Sporangia borne in laminal or marginal sori"	56
56	"Mature fronds simple or deeply pinnatifid, not pinnate; mainly epiphytic ferns"	57
56	"Mature fronds 1–3-pinnate; terrestrial ferns"	58
57	"Frond 1–3 cm tall; lamina simple; sori sunken in submarginal grooves parallel to midrib"	Scleroglossum
57	"Frond 30–80 cm tall; lamina deeply pinnatifid; sori not sunken, oblique to midrib"	Colysis
58	"Rhizome climbing or scrambling; fertile frond much narrower than sterile frond, with linear segments 15–20 cm long and 2–3 mm wide"	Stenochlaena
58	"Rhizome creeping or erect; fronds not strongly dimorphic"	59
59	"Rhizome with clathrate scales; lamina densely covered in hairs; sori laminal, growing on free veins"	Pleurosorus
59	"Rhizome with dark bristles or basally attached, non-clathrate scales; lamina glabrous or variously hairy; sori marginal, or if laminal, the pinnae glabrous and sori either growing on free or anastomosing veins, or occupying a continuous band between midrib and margin"	Adiantaceae
60	"Sporangia massed along minor veinlets of lower pinnules of primary pinnae, becoming confluent; stipes with persistent, basal, stipular expansions"	Todea
60	"Sporangia not massed along minor veinlets of lower pinnules of primary pinnae; stipes lacking persistent, basal, stipular expansions"	61
61	"Rhizome with thick, fleshy prop roots; fronds 1–4 m tall"	Acrostichum
61	"Rhizome without prop roots; most or all fronds less than 1 m tall"	62
62	"Rhizomes mostly creeping or climbing, dorsiventral; stipes articulated to the rhizome or ±decurrent on it"	Lomariopsidaceae
62	"Rhizomes mostly erect, often forming a short trunk; stipes not articulated to the rhizome"	Blechnaceae