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[ This set of files is an HTML version of a manuscript that was prepared sometime in mid 1980s, as working documents to help identify Papuasian pteridophytes. It is presented here essentially as it was at the time, and users should be aware that references and collections made over the last 14 years have not been added and that taxonomy and nomenclature has not been updated accordingly. An update is intended, as time permits. - jrc ]


J.R. Croft


The following keys cover the genera of ferns and fern allies recorded from Papuasia, the geographical area including the political units of Papua New Guinea, Irian Jaya and the Solomon Islands. All genera except Thayeria and Matonia, known from single collections from Irian Jaya, have been collected in Papua New Guinea; these two genera may turn up with more intensive collection; all genera known from the Solomon Islands are also known from Papuan New Guinea and the New Guinea mainland.

This is a complilation of keys from various sources. The basic architecture of the main key to families is that of Holttum (1959 - General key No. 1). This key was selected because it relies less heavily on the vasculature of the stipe than his Key No. 2, a character not readily evident in dried material, and works well both in the field and in the herbarium. It has been modified to exclude those genera known not to occur in Papuasia, and expanded to include the fern-allies, and to accommodate a few deficiencies of the original key when applied to the Papuasian flora. For purely practical reasons the families have been named in accordance with Holttum's arrangement of Pichi-Sermolli's system presented in the 8th edition of Willis' "Dictionary of the flowering plants and ferns" (Willis 1973).

In many instances pteridologists disagree over the allocation of genera to families and a complete resolution of these difference is unlikely in the near future. Some of the various alternatives are indicated in the notes after each family key.

For a sequential arrangement of the pteridophytes see Crabbe, Jermy and Mickel (1975). This arrangement has been adopted by several major herbaria, although controversy still exists over the rank and composition of some of the groups (e.g. Pichi Sermolli 1977; Brownsey et al. 1985).

The keys to genera are fundamentally those of Holttum (1959), expanded to include the improvements of subsequent revisions, and those genera added to the flora as a result of recent collections. The most notable contribution here is Holttum's elaboration of the Thelypteridaceae.

Bracketed keys have been used for the practical considerations of ease of format and conservation of space. In the long keys headings have been inserted to make the keys easier to use for those familiar with pteridophytes. Those who are unsure should follow through each step in turn.

General References:

Van Alderwerelt van Rosenburg, C.R.W.K. 1908. Malayan ferns. Handbook to the determination of the ferns of Malayan Islands. Batavia.

Van Alderwerelt van Rosenburg, C.R.W.K. 1915. Malayan fern allies. Handbook to the determination of fern allies of the Malayan islands. Batavia.

Van Alderwerelt van Rosenburg, C.R.W.K. 1917. Malayan ferns and fern allies. Suppliment 1. Batavia.

Bierhorst, D.W. 1971. Morphology of vascular plants. Macmillan, New York.

Ching, R.C. 1940. A natural classification of the family Polyodiaceae. Sunyatsenia 5: 201 - 68.

Christensen, C. 1906. Index Filicum. (reprinted 1973, Otto Koeltz, Koenigstein.)

Christensen, C. 1913. Index Filicum. Supplementum 1906 - 1912. (reprinted 1973, Otto Koeltz, Koenigstein.)

Christensen, C. 1917. Index Filicum. Supplement preliminaire pour les annes 1913, 1914, 1915, 1916. (reprinted 1973, Otto Koeltz, Koenigstein.)

Christensen, C. 1934. Index Filicum. Supplementum tertium pro annis 1917 - 1933. (reprinted 1973, Otto Koeltz, Koenigstein. (for suppl. IV see Pichi-Sermolli 1965).

Copeland, E.B. 1929. The oriental genera of the Polypodiaceae. Un. Cal. Publ. Bot. 16: 45 - 128.

Copeland, E.B. 1947. Genera filicum, the genera of ferns. Ronald Press, New York. i - xiv, 1 - 247, pl. 1 - 10.

Crabbe, J.A., Jermy, A.C. & Mickel, J.T. 1975. A new generic sequence for the pteridophyte herbarium. Brit. Fern Gaz. 11: 141 - 162.

Holttum, R.E. 1949. The classification of ferns. Biol. Rev 24: 267 - 296.

Holttum, R.E. 1959 1. Introductory note; 2. List of Malaysian Pteridophytes; 3. The morphology of ferns; 4. General key No 1 to Pteropsida; 5. General key No 2 to Pteropsida; 6. Keys to the genera of Pteropsida; 7. Bibliography. Fl. Males. ser. 2 a: I - XXIII.

Jermy, A.C., Crabbe, J.A. & Thomas, B.A. (eds.) 1973. The phylogeny and classification of ferns. Suppl. 1, Bot. J. Linn. Soc. 67.

Pichi-Sermolli, R.E.G. 1965. Index Filicum. Supplementum quartum pro annis 1934 - 1960. I.U.B.S., Utrecht.

Pichi-Sermolli, R.E.G. 1970. A provisional catalogue of the family names of living pteridophytes. Webbia 25: 219 - 297.

Pichi-Sermolli, R.E.G. 1973. Historical review of the higher classification of the Filicopsida. In Jermy, A.C., Crabb, J.A. & Thomas, B.A. eds, Phyllogeny and classification of the ferns. Suppl. 1 Bot. J. Linn. Soc. 67: 11 - 40, f. 1 - 8, pl. 1 - 19.

Pichi-Sermolli, R.E.G. 1977. Tentamen pteridophytorum genera in taxanomicum ordinam redigendi. Webbia 31: 315 - 512.

Willis, J.C. 1973. A dictionary of the flowering plants and ferns. Ed. 8 (edited by H.K. Airy Shaw). Cambridge Univ. Press. i-xxii, 1 - 1245, i-lxvi. (All pteridophyte entries and Introduction to Pteridophyta xiii - xvi by R.E. Holttum)

Regional references:

Brownlie, G. 1969. Flore de la Nouvelle-Caledonie et dependances. 3. Pteridophytes. Mus. Nat. Hist. Natur., Paria. 1 - 307, pl. 1 - 39.

Brownlie, G. 1977. The pteridophyte flora of Fija. Beih. Nova Hedwigia 55: 1 - 397, pl. 1 - 44.

Brownsey, P.J., Given, D.R. & Lovis, J.D. 1985. A revised classification of the New Zealand pteridophytes with a synomymic checklist of species. New Zealand J. Bot. 23: 431 - 489.

Copeland, E.B. 1958 - 1960. Fern flora of the Philippines. Vol. 1 - 3. Manila Bureau of Printing. 1 - 555.

Croft, J.R. 1985. Ferns and fern allies. In Leach, G.J. & Osborne, P.L., Fresh water plants of Papua New Guinea. pp. 32 - 74, f. 6 - 13. Univ. P.N.G. Press, Port Moresby.

Holttum, R.E. 1954 revised 1965. Ferns of Malaya. A revised flora of Malaya. Volume 2. 1 - 643. Incl. Appendix by I. Manton, Cytological notes on 100 species of Malayan ferns. Govt. Printer, Singapore.

Johns, R.J. & Bellamy, A. 1979. Ferns and fern allies of Papua New Guinea. P.N.G. Office of Forests. (checklist of genera, treatments of several families; continuing series)

Jones, D.L. & Clemesha, S.C. 1976. Australian ferns and fern allies, with notes on their cultivation. Reed pty ltd, Sydney. 1 - 294, f. 1 - 252, pl. 1 - 60.

Jones, D.L. & Clemesha, S.C. 1981. Ditto. 2nd edition. 1 - 232, f. 1 - 297, pl. 1 - 60.

Wagner, W.H. & Grether, D.F. 1948. Pteridophytes of the Admiralty Islands. Un. Cal. Publ. Bot. 23: 17 - 110.

The Pteridophytes of Papuasia

Terrestrial, epiphytic, rupestral or aquatic (not marine) vascular plants of mostly moderate stature with distinct alternating generations: the gametophyte small and relatively short-lived and avascular producing the sexual organs antheridia (male) and archegonia (female); the sporophyte the dominant generation, large and vascular, producing asexual spores which develop into the gametophyte.

In Papuasia there are 187 genera of pteridophytes covering c. 1700 - 1800 species; undescribed taxa may push this figure as high as 2000. Worldwide there are 9000 - 12000 species in c. 350 genera. The allocation of families is always a matter of dispute among pteridologists the number ranging from c. 60 to less than 10; this treatment divides the genera among 44 families, largely by treating all families in their narrowest sense.

The pteridophytes are generally considered to be an unnatural collection of several unrelated groups that should have equal status to the Bryophyta (mosses and liverworts) and the Spermatophyta (seed-plants). There are 4 such groups: Psilopsida (Psilotum and Tmesipteris); Lycopsida (Lycopodium, Selaginella, Isoetes); Sphenopsida (Equisetum); Filicopsida (true ferns). However, in this treatment, for purely practical purposes, these divisions are ignored.

The descriptions and keys in this treatment cover only the sporophyte generation, since this is the stage that most people see and are familiar with. The gametophyte and sexual stages of pteridophytes are for the most part small and short-lived, and although they certainly offer useful diagnostic characters, they have only been studied for a very small proportion of the species.

Note: In this key the numbers in parentheses after key couplet numbers indicate the preceding couplet, thus "49 [42]" means that a choice in couplet 42 lead to couplet 49. This is to enable checking by working backwards in confusing situations.

List of families with keys to genera

Key to families

1 Leaves microphyllous, simple or once-divided, with a single vein and no petiole (fern allies)... ...2
Leaves megaphyllous, variously divided with several to many veins (true ferns)... ...6
2 [1] 2 - 3 (rarely 4) sporangia fused into a single synangium, and borne in the axils of minute and bract-like or larger and leaf-like bifid sporophylls; homosporous; axis not differentiated into roots... Psilotaceae
Sporangia free, borne axillary on sporophylls which are often condensed into strobili; homosporous or heterosporous; axis with differentiated roots... ... 3
3 [2] Plants cylindrical with regular sheathed nodes, scariose, bract-like leaves borne in a singe whorl at each node, the stem photosynthetic, hollow, containing many silica crystals; homosporous Equesitaceae
Plants not cylindrical, bearing expanded photsynthetic leaves; homosporous or heterosporous ... 4
4 [3] Aquatic (occasionally terestrial) rosette herbs with a thickened, compact, corm-like axis; leaves linear with 4 large longitudinal air-chambers Isoetaceae
Terrestrial or epiphytic herbs, never rosettes nor corm-like, axis elongate and mostly branched; leaves short, without air-chambers ... 5
5 [4] Heterosporous; leaves ligulate, 4-ranked, decussate but mostly dorsiventral with 2 larger rows beneath and 2 smaller rows above; stem often supported by stilt-like rhizophores at intervals... Selaginellaceae
Homosporous; leaves eligulate, mostly arranged in close spirals, sometimes decussate, sometimes dorsiventrally flattened with all but 2 rows reduced; supported by clusters of roots Lycopodiaceae
6 [1] Aquatic plants or swamp plants, free floating, submerged or emergent, spending significant periods in or under water ... 7
Land plants or epiphytes, if river-side plants then immersed for only brief periods during floor ... 15
7 [6] Plants free-floating; leaves or leaf-like appendages simple or bilobed, smallish; plants spreading vegetatively by fragmentation ... 8
Plants rooted in soil, mud, or on rocks, or on floating mats of vegetation, sometimes some plants free-floating as well; fronds large and pinnately divided; vegetative reproduction sometimes by marginal proliferous buds ... 9
8 [7] Expanded leaves large (longer than 1 cm), simple, borne in opposite pairs on the surface of the water, a third leaf finely divided and root-like beneath the water, bearing the sporocarps Salviniceae
Leaves small (c. 1 mm long), bilobed, scale-like and overlappping, roots thin and thread-like Azollaceae
9 [7] Leaves divided into 4 equal, +/- radial lobes at the end of a long stalk; heterosporous, the spores borne in a capsule-like sporocarp Marsileaceae
Leaves (fronds) pinnate or pinnately lobed or compound, not 4-partite; homosporous, the spores borne in thin-walled sporangia ... 10
10 [9] High-climbing epiphytes starting from the ground, uncommonly scrambling and thicket-forming in the absence of trees; fronds pinnate, sterile with close parallel venation with a single series of very narrow areoles along the midrib, fertile very narrow and completely covered by sporangia Blechnaceae
Ground ferns with radial or creeping rhizomes, in one case thicket-forming but never epiphytic; fronds pinnatifid to pinnately compound, veins freely anastomosing, or in pinnate groups, anastomosing or not, sporangia borne in discrete or continuous sori on non-contracted fronds, or if on contracted fronds, protected by the reflexed margin of the lamina ... 11
11 [10] Rhizome +/- erect, sometimes decumbent, radial, woody or fleshy, plants not stoloniferous; venation freely reticulate without included free veinlets, not in pinnate groups; sporangia completely covering the lower surface of pinnae, or on contracted fertile fronds and protected by the reflexed margin ... 12
Rhizome creeping, not radial, or if thin and radial plants spreading by wiry stolons; venation in pinnate groups, free or uniting, or reticulate with included free veinlets; sporangia borne in discrete +/- round sori ... 13
12 [11] Large erect plants, stem stout, erect, woody; sporangia completely covering the entire lower surface of the upper few pinnae, the pinnae not contracted Pteridaceae
Plants of moderate size, stem small, fleshy, with numerous air canals; sporangia borne on contracted fertile fronds and protected by the reflexed margin Parkeriaceae
13 [11] Fronds pinnate; veins forked, free and +/- parallel to the margin or in pinnate groups, free or uniting with neighbouring groups; sori small, often protected by an indusium ... 14
Fronds pinnately lobed or simple with entire margins; veins freely reticulate, with included free veinlets; sori large not protected by indusia Polypodiaceae
14 [13] Sterile pinnae mostly entire or obscurely toothed, jointed to the rachis; veins forked, free and +/- parallel to the margin; plants propagating by wiry rhizomes; sori indusiate Oleandraceae
Pinnae deeply or shallowly toothed, not articulate to the rachis; veins in pinnate groups in the lobes, free or united with veins of adjacent groups to form a single excurrent vein; plants not stoloniferous, sometimes with proliferating buds along the rachis; sori indusiate or not Thelypteridaceae
15a [6] Epiphytes, not climbing from the ground ... 16
Terrestrial plants, rock plants or climbers starting from the ground ... 42
16 [15] Fronds simple, not over 2 mm wide, with a single vein, or with a few simple lateral soriferous veins close to the main vein Vittariaceae
Fronds variously branched, or, if simple, with a more complex venation or lamina 1 cell thick ... 17
17 [16] Lamina filmy, 1 cell thick, apart from the midribs of the segments Hymenophyllaceae
Lamina throughout more than 1 cell thick ... 18
18 [17] Sporangia imbedded in a slender cylindrical appendage attached to the surface of the frond Ophioglossaceae
Sporangia grouped in sori on, or sunken in, the surface of the frond ... 19
19 [18] Sori not indusiate, sometimes variously protected in pockets, grooves or folds of the lamina ... 20
Sori protected by an obvious indusium ... 33
20 [19] Sporangia in discrete sori, not acrostichoid (i.e. not spreading over the entire surface of the frond) ... 21
Sporangia acrostichoid, completely covering the whole or part of the the frond ... 32
21 [20] Sori superficial, not in pockets or grooves ... 22
Sori immersed in pockets or grooves which are sometimes marginal ... 28
22 [21] Fronds simple, pinnatifid or pinnate; if pinnate, then the pinnae not articulate to the rachis ... 23
Fronds pinnate, pinnae articulate to the rachis ... 27
23 [22] Veins copiously reticulate ... 24
Veins not, or only slightly anastomosing ... 25
24 [23] Stipes articulate to phyllopodia or to the rhizome; rhizome scales mostly peltate-based; spores monolete Polypodiaceae
Stipes not articulate; rhizome scales mostly basally attached; spores trilete (Loxogramme) Polypodiaceae
25 [23] Frond pinnate with dimidiate pinnae; rhizome scales thin and clathrate Hemionitidaceae
Pinnae or lobes +/- even-sided, not dimidiate; rhizome scales opaque or clathrate ... 26
26 [25] Frond and stipe +/- hairy; spores trilete Grammitidaceae
Frond and stipe not hairy; spores monolete Polypodiaceae
27 [22] Pinnae entire Polypodiaceae
Pinnae toothed or lobed Oleandraceae
28 [21] Sori in pockets or depressions, +/- circular ... 29
Sori elongate in grooves ... 30
29 [28] Veins anastomosing, or, if free, then fronds not hairy Polypodiaceae
Veins free, fronds +/- hairy Grammitaceae
30 [28] Soral grooves all evenly oblique to costs Polypodiaceae
Soral grooves marginal or intramarginal or parallel to the margin, or uneven in direction, sometimes anastomosing ... 31
31 [30] Scales entirely opaque, usually brown Grammitidaceae
Scales dark grey or nearly black, strongly clathrate (cells translucent with dark transverse cell walls) Vittariaceae
32 [20] Veins much anastomosing; spores without a perispore Polypodiaceae
Veins free, or slightly anastomosing near the edge; spores with a perispore Lomariopsidaceae
33 [19] Sori elongate along the veins Aspleniaceae
Sori short, on veins, or at the ends of veins, or elongate along the edge of the lamina ... 34
34 [33] Sori elongate along the veins Aspleniaceae
Sori at the ends of veins, close to or remote from the edge of the lamina ... 37
35 [34] Pinnae articulate to the rachis Oleandraceae
Pinnae +/- confluent with the rachis ... 36
36 [35] Sorus protected by an indusium opening towards the margin of the lamina; rhizome portostelic Lindsaeaceae
Sorus protected by a reflexed edge of the lamina; rhizome solenostelic Dennstaedtiaceae
37 [34] Fronds articulate to the rhizome ... 38
Fronds +/- confluent with the rhizome ... 40
38 [37] Sori at the ends of the veins, near the edge of the lamina; fronds mostly variously divided ... 39
Sori mid-way to the margin or close to the costa; frond simple Oleandraceae
39 [38] Pinnae, if present, not jointed to the rachis Davalliaceae
Fronds pinnate, the pinnae jointed to the rachis Oleandraceae
40 [37] Indusium thin, circular, peltate Dryopteridaceae
Indusium reniform, pouch-shaped or attached at the base, not peltate ... 41
41 [40] Pinnae jointed to the rachis Oleandraceae
Pinnae not jointed to the rachis Davalliaceae
42 [15] High-climbing with rhizome starting from the ground ... 43
Terrestrial or rock plants ... 49
43 [42] Fronds thin and filmy, lamina 1 cell thick, several-times pinnatifid; sori in a marginal cup or tube Hymenophyllaceae
Fronds many cells thick, often tough, mostly pinnate, uncommonly more divided; sori protected by reflexed margin, or entirely covering the surface of the frond., or round, superficial and exindusiate ... 44
44 [42] Sporangia in discrete, +/- round sori, the sori superficial, or somewhat immersed, remote from the margin, or the sori elongate along the veins ... 45
Sporangia entirely covering the surface of the frond, or sorum elongate sorus along the margin ... 47
45 [44] Fronds pinnate with pinnae articulate to the rachis, the pinnae toothed or lobed; sori superficial, circular Oleandraceae
Fronds simple or pinnatifid, if pinnate then the pinnae not articulate to the rachis, margins entire or at most finely toothed; sori circular, elliptic, or elongate, sometimes sunken into the lamina ... 46
46 [45] Veins copiously anastomosing; sori round, elliptic, rarely elongate, exindusiate Polypodiaceae
Veins free; sori elongate and parallel along the veins, indusiate Aspleniaceae
47 [44] Sorus elongate along the margin, protected by a relfexed flap of the margin Dennstaedtiaceae
Sorus acrostichoid, completely covering lower surface of contracted fertile fronds ... 48
48 [47] Rhizome +/- radia; veins anastomosing in a narrow series of areoles elongate along the costa (best seen at the apex of the pinna) Blechnaceae
Rhizome dorsiventral; veins either free to the margin, or freely anastomosing Lomariopsidaceae
49 [42] Caudex often massive, erect, fleshy; stipes succulent with stipule-like outgrowths at their bases; 2 - 3-pinnate, bases of pinnae swollen; sporangia large and arranged in two short adjacent rows along a vein, sometimes fused into a single unit ... 50
Not this combination of characters; if caudex and stipes fleshy, then not massive and lacking large auricles; sporangia not so arranged ... 51
50 [49] Sporangia in each group united laterally into a +/- prism-shaped synangium Marattiaceae
Sporangia in each group almost free, appearing as two adjacent rows astride a vein Angiopteridaceae
51 [49] Lamina 1 or 2 cells thick apart from the midribs of the segments; stomata absent ... 52
Lamina several to many cells thick throughout; stomata present ... 53
52 [51] Sporangia attached to elongate slender receptacles in funnel- or cup-shaped pockets at the ends of the veins; caudex always small or creeping Hymenophyllaceae
Sporangia scattered on the surface of the veins; caudex stout and tree-like Osmundaceae
53 [51] Apex of caudex or rhizome and bases of stipes hairy or bristly or apparently naked; flat scales lacking ... 54
Apex of caudex or rhizome and bases of stipes, at least when young, scaly; sometimes also hairy ... 68
54 [53] Caudex massive and erect, in a few cases tree-like, or +/- decumbent, radially organised, apex above ground bearing a close clump of fronds ... 55
Caudex of rhizome otherwise, small, often creeping, usually entirely below the ground ... 58
55 [54] Apex of caudex densely hairy; sori protected by reflexed lobe of the lamina and an inner cup-like indusium ... 56
Apex of caudes naked, sometimes with a mucilaginous slime; sori exindusiate, superficial, covering the lower surface of the contracted fertile fronds ... 57
56 [55] Lamina bipinnate with shallowly lobed pinnae; caudex short; stipe with 2 vascular strands forming an X-shaped strand at the base of the frond Cystodiaceae
Lamina 3 - 4-pinnate, or if bipinnate the pinnules deeply lobed; caudex sometimes arborescent; vascular strands several or a single arc, not forming an X-shaped strand Dicksoniaceae
57 [56] Fronds simply pinnate; aerophores (projections of aerating tissue) at the base of the stipe, sometimes also at the base of the pinnae; sori acrostichoid, densely covering the entire lower surface of the contracted linear fertile pinnae, all pinnae fertile. Plagiogyriacae
Fronds pinnate or more divided; aerophores lacking; sori not acrostichoid, scattered over the surface of +/- contracted fertile pinnae, only a few pairs of lateral pinnae fertile, deeply lobed Osmundaceae
58 [54] Fertile part of frond not leaf-like, erect, branched or linear, attached to the base of the leafy part Ophioglossaceae
Fertile frond or part of frond leaf-like, sometimes reduced in size as compared with the sterile ... 59
59 [58] Fronds palmately divided, leaflets 3 or 5; veins anastomosing; sporangia large and thick-walled, united into a radial synangium Christenseniaceae
Fronds otherwise, if appearing palmate then leaflets more than 5, of pinnately lobed; sporangia may be radially arranged, sometimes with an indusium, not fused into a circular synangium ... 60
60 [59] Veins copiously anastomosing, with free veins in the areoles ... 61
Veins in most cases free and parallel, where anastomosing, no free veins in the areoles ... 62
61 [60] Fronds dimorphous, sterile broad and often with 2 broad lobes at the apex, fertile narrow and acrostichoid with the sorus completely covering the lower surface Cheiropleuriaceae
Fronds uniform, with two major lateral leaflets which may be further incised in a +/- radial manner; sori numerous, small and round, scattered over the lower surface of the frond Dipteridaceae
62 [60] Sori quite superficial on the lower surface of the lamina, or in a marginal groove ... 63
Sori at the ends of veins or on special appendages ... 65
63 [62] Sori completely covered by an indusium; fronds slender, trailing Matoniaceae
Sori exindusiate ... 64
64 [63] Fronds repeatedly pseudodichotomous, with a dormant apex between each pair of lateral branches, the ultimate branches +/- pectinate, apparently capable of indefinite growth Gleicheniaceae
Fronds otherwise, ultimate branches not pectinate, not capable of indefinite growth Heminionitidaceae
65 [62] Sporangia on special appendages at the ends of veins of the leaflets, or attached near the apex of the frond or its branches Schizaeaceae
Sporangia in sori at the ends of single veins, or uniting the ends of several veins, not on special appendages ... 66
66 [65] Sori at the ends of single veins, exindusiate, sporangia mixed with glandular trichomes; apex of rhizome with hairs embedded in a mucilaginous secretion Monachosoraceae
Not as above, sori mostly indusiate, or proteted by the reflexed margins, not glandular; no such secretions ... 67
67 [66] Indusium attached at the base of the sorus, flat and opening towards the margin, the margin flat and not reflexed Lindsaeaceae
Sorus protected by a reflexed margin of lamina and a thinner inner indusium, sometimes exindusiate, or in a cup-shaped indusium at the ends of the veins Dennstaedtiaceae
68 [53] Sporangia acrostichoid, entirely covering all or part of the lower surface of the fertile frond ... 69
Sporangia not acrostichoid, sori discrete, and/or indusiate, or variously elongate ... 74
69 [68] Rhizome dorsiventral, creeping on rocks ... 70
Rhizome not dorsiventral, often massive, bearing a tuft of fronds at its apex ... 71
70 [69] Veins free, or if anastomosing then the free veins nearly all pointing towards the margin; spores with a perispore Lomariopsidaceae
Veins much anastomosing with the free veins in the areoles pointing in all directions; spores lacking a perispore Polypodiaceae
71 [69] Only the upper pinnae fertile; veins copiously anastomosing with no free veins in the areoles Pteridaceae
The whole frond fertile; in the sterile frond veins free or anastomosing otherwise ... 72
72 [71] Veins free in sterile fronds, or with a single narrow row of costal areoles (best seen at the apex of the pinnae) ... 73
Veins copiously anastomosing is sterile fronds, often with included free veinlets Hypoderriaceae
73 [72] Fertile fronds simply pinnate Blechnaceae
Fertile fronds bipinnate Hypoderriaceae
74 [68] Sorus elongate along edge of lamina, continuous or nearly so ... 75
Sorus otherwise, short, if elongate then not along edge of lamina ... 79
75 [74] Edge of lamina reflexed, protecting sori ... 76
Edge of lamina not reflexed, the sorus protected by an indusium attached at the base of the sorus and opening towards the margin of the lamina Lindsaeaceae
76 [75] Rhizome creeping or scandent Dennstaedtiaceae
Rhizome compact, generally erect ... 77
77 [76] Rachis grooved on the upper surface, the groove open to admit the groove of the midrib of the pinnae (in species with simple, unlobed pinnae the edge of the rachis-groove does not open to admit grooves of costae, the lamina not decurrent along edge of rachis groove) Pteridaceae
Rachis not so grooved, or if grooved then the edtge of the lamina may be decurrent along the edge of the rachis groove ... 78
78 [77] Fertile lobes of frond much broader than sterile, the whole of each margin bearing a broad, thin, reflexed indusium Cryptogrammitaceae
Fertile lobes not much broader than sterile, reflexed margin not continuous along larger fertile lobes, nor very broad Sinopteridaceae
79 [74] Sorus elongate, continuous along each side of the costa of the pinna Blechnaceae
Sorus otherwise, discrete, short, or if elongate then elongate along the veins ... 80
80 [79] Sporangia on the surface of darkened, reflexed marginal lobes Adiantaceae
Sporangia not on such lobes ... 81
81 [80] Sorus elongate along the veins, at least some of them ... 82
Sori short, or not elongate along the veins ... 91
82 [81] Sorus protected by an indusium ... 83
Sori lacking indusia ... 87
83 [82] Sorus symmetrically divided by the line of the vein ... 84
Sorus asymmetric or on one side of the vein ... 85
84 [83] Rachis grooved, the groove open to admit the groove of the branch; scales lacking superficial hairs Dryopteridaceae
Rachis somewhat grooved, the groove not open to admit the grooves of the pinnae; scales bearing superficial hairs Thelypteridaceae
85 [83] Sori along the outer veins of the costal or costular areoles Blechnaceae
Sori otherwise, mostly elongate along veins running towards the margin ... 86
86 [85] Two vascular strands at the base of the stipe, uniting upwards to form a single X-shaped strand; scales mostly clathrate Aspleniaceae
Two vascular strands at the base of the stipe, uniting upwards to form a single U-shaped strand; scales not clathrate Athyriaceae
87 [82] Sori spreading along all the veins of the lower surface ... 88
Sori not spreading along all veins ... 89
88 [87] Slender unicellular hairs present on the frond and on the scales Thelypteridaceae
Slender unicellular hairs lacking on all parts of the plant Hemionitidaceae
89 [87] Several vascular bundles in the stipe Hypoderriaceae
Two vascular bundles at the base of the stipe, uniting upwards ... 90
90 [89] White waxy powder on lower surface of lamina Hemionitidaceae
No waxy powder present Athyriaceae
91 [81] Sori at the ends of veins, at or close to the edge of the lamina, each in the base of a cup, or protected by an indusium attached below it, or by the reflexed edge of the lamina ... 92
Sori not at the ends of veins, or if so, not close to the edge of the lamina ... 95
92 [91] Sori each in the base of a cup Dennstaedtiaceae
Sori protected by indusia or by the reflexed edge of the lamina ... 93
93 [92] Sori protected by indusia opening outwards ... 94
Sori protected by a reflexed edge of the lamina Sinopteridaceae
94 [93] Pinnae articulate to the rachis Oleandraceae
Pinnae confluent with rachis Lindsaeaceae
95 [91] Rhizome dorsiventral ... 96
Rhizome not dorsiventral ... 99
96 [95] Sori lacking indusia ... 97
Sori indusiate ... 98
97 [96] Fronds lacking dormant apices, incapable of indefinite growth Polypodiaceae
Fronds with some dormant apices, often capable of indefinite growth Gleicheniaceae
98 [96] Fronds simple Oleandraceae
Fronds pinnately branched Davalliaceae
99 [95] Fronds simple and jointed at the base, or pinnate and pinnae jointed to the rachis Oleandraceae
Fronds otherwise, neither jointed at the base, nor the pinnae jointed to the rachis ... 100
100 [99] Tree-ferns; sporangia with a complete, oblique annulus; many vascular bundles in stipe Cyatheaceae
Not tree ferns, although caudex sometimes quite long; annulus longitudinal, interrupted; vascular bundles in a simple ring (except Pleocnemia), or 2 uniting upwards ... 101
101 [100] Rachis grooved, groove open to admit branch-rachis of pinna ... 102
Rachis not grooved, or if grooved, then the groove not open to admit branch-rachis of pinna ... 103
102 [100] Several vascular bundles in stipe ... Dryopteridaceae
Two vascular bundles at the base of the stipe, uniting upwards to form a single U-shaped strand Athyriaceae
103 [101] Hairs, if present, multicellular; scales lacking superficial hairs or glands ... 104
Hairs unicellular; scales bearing superficial hairs or glands Thelypteridaceae
104 [103] Several vascular bundles in stipe Hypoderriaceae
Two vascular bundles at the base of the stipe uniting upwards to form a single vascular strand Athyriaceae

Updated November 1999 by Jim Croft ( )