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Family Key Blechnaceae Isoetaceae Oleandraceae Polypodiaceae Salviniaceae
Azollaceae Equisetaceae Marsileaceae Parkeriaceae Pteridaceae Thelypteridaceae


Key the Papuasian families of aquatic ferns and their allies

The following key is a traditional dichotomous key and is based on the more conspicuous characters of sporophyte generation. The key can be navigated by the links at each couplet and each family name leades to the coresponding family treatment.

1 Plants free floating... ... 2
Plants rooted in the mud or soil beneath water, or in floating mats of vegetation, or on banks beside water... ... 4
2 Leaves simple or bilobed, stem short- or long-creeping, +/- hairy, plants spreading vegetatively by fragmentation; spores of 2 sizes... ... 3
Leaves 2 - 3 - pinnately lobed, stem (rhizome) short and radial, scaly; sterile fronds sometimes spreading vegetatively by marginal proliferous buds; spores uniform... Parkeriaceae
3 Expanded leaves large (1 cm or more), simple, borne in opposite pairs, on the surface of the water, a third lead finely divided and root-like beneath the water bear the sporocarps... Salviniaceae
Leaves small (c. 1 mm), bilobed, scale-like and overlapping, roots thin and thread-like... Azollaceae
4 Plants fully submerged, rarely exposed for short periods during dry spells; leaves simple, numerous, long and quill-like, borne on a compact, radial, corm-like rootstock; spores or 2 sizes... Isoetaceae
Plants generally emergent, or at water margin, or on floating mats of vegetation; leaves compound, or lobed, or reduced to scale-like teeth... ... 5
5 Plants erect and rush-like, stems pointed and finely grooved, green, leaves reduced to a whorl of minute brown teeth at each node; spores green, borne in a terminal cone... Equisetaceae
Plants not rush-like, stems not jointed, fully expanded leaves present; spores brown or black, produced in variously protected sori or sporocarps, not cones... ... 6
6 Leaves divided into 4 equal +/- radial lobes at the end of a long stalk; spores bornein a capsule-like sporocarp, of 2 sizes... Marsileaceae
Leaves (fronds) pinnately lobed or compound, not 4-patite; spores borne in thin-walled sporangia variously grouped into sori, uniform... ... 7
7 High-climbing epiphytes starting from the ground, less commonly 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... ... 8
8 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... ... 9
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... ... 10
9 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 or spongy, with numerous air canals; sporangia borne on contracted fertile fronds and protected by the reflexted margin... Parkeriaceae
10 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... ... 11
Fronds pinnately lobed or simple with entire margins; veins feely reticulate, with included free veinlets; sori large, not protected by indusia... Polypodiaceae
11 Sterile pinnae mostly entire or obscurely toothed, articulate 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 articlate 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; sori indusiate or not... Thelypteridaceae