Artificial Key to Families of Ferns and Allies
Couplet 1
1. Leaves long and quill-like, all basal.... 3. ISOETACEAE
1. Leaves (fronds) broad, flat, and fern-like, more or less pinnatid, divided or entire, or, narrow, small, and scale-like, or larger, divided and clover-like. go to 2.
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Couplet 2
2. Leaves narrow, small, and scale-like, or larger, divided, and clover-like. goto 3.
2. Leaves (fronds) broad, flat, and fern-like, more or less pinnately or ternately divided or entire. goto 7.
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Couplet 3
3. Leaves 4-foliolate, clover-like. 14. MARSILEACEAE
3. Leaves subulate, scale-like. goto 4.
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Couplet 4
4. Leaves whorled, forming sheaths at the nodes of the jointed stem; sporangia in terminal spikes.... 4. EQUISETACEAE
4. Leaves not whorled; stems not conspicuously jointed. goto 5.
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Couplet 5
5. Plants aquatic, floating, small, branched, and coral-like. 15. AZOLLACEAE
5. Plants not aquatic. goto 6.
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Couplet 6
6. Plants not resembling mosses, the stems often long and creeping; spores all alike. 1. LYCOPODIACEAE
6. Plants small and moss-like; spores of two kinds (microspores and megaspores). 2. SELAGINELLACEAE
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Couplet 7
7. Sporangia without an annulus, splitting open by a vertical slit; fronds dimorphic or at least the fertile and sterile divisions very dissimilar. goto 8.
7. Sporangia with an annulus, splitting open by a transverse cleft on one side, the walls 1 cell thick; fronds similar or dimorphic. goto 9.
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Couplet 8
8. Sporangia on special modified fronds or on much modified divisions at the summit or middle of the sterile frond; walls of the sporangia 1 cell thick; rootstocks stout; fronds in large clumps. 6. OSMUNDACEAE
8. Sporangia aggregated in spikes or panicles apparently at the summit of the stem, with the leaf-like sterile part lateral or basal; walls of the sporangia several cells thick; rootstocks practically wanting; fronds not in clumps. 5. OPHIOGLOSSACEAE
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Couplet 9
9. Fronds dimorphic, the sori (with indusia) inclosed in globular or necklace-like parts of the contracted fertile fronds. 12. DRYOPTERIDACEAE
9. Fertile and sterile fronds similar. goto 10.
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Couplet 10
10. Sori elongate, in 1 row on each side of and adjacent to the costae, chainlike, extending the length of the pinnae; indusia introrse, facing away from the margins. 10. BLECHNACEAE
10. Sori elongate to round, if elongate and parallel to costae then not immediately adjacent to them; indusia, when present, usually extrorse, opening variously. goto 11.
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Couplet 11
11. Indusia cuplike, attached proximally or sometimes along sides, or formed by revolute blade margins. 8. DENNSTAEDTIACEAE
11. Indusia linear, reniform, peltate or absent, rarely cuplike, sometimes replaced by false indusium formed by reflexed or revolute blade margins. goto 12.
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Couplet 12
12. Sori marginal, the indusium appearing to consist of the reflexed margin of the frond; rootstocks creeping. 7. PTERIDACEAE
12. Sori dorsal, though sometimes near the margin; indusium independent of the margin of the frond. goto 13.
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Couplet 13
13. Sori elongated. goto 14.
13. Sori orbicular or nearly so. goto 15.
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Couplet 14
14. Fronds simple or 1-pinnate. 11. ASPLENIACEAE
14. Fronds 2-pinnate. 12. DRYOPTERIDACEAE
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Couplet 15
15. Fronds articulated with the creeping rootstocks, 1-pinnatifid, the divisions confluent at the base; sori naked. 13. POLYPODIACEAE
15. 1-pinnate the divisions distinct; rootstocks creeping or not creeping; sori naked or covered. goto 16.
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Couplet 16
16. Costae and veins bearing hairs sparse to dense, needlelike (or sometimes stellate) transparent hairs; petiole in cross section at the base with 2 crescent-shaped vascular bundles. 9. THELYPTERIDACEAE
16. Costae and veins lacking needlelike, transparent hairs, sometimes with brown hairlike scales or glandular trichomes; petiole base in cross section with 2 or more round or oblong vascular bundles. 12. DRYOPTERIDACEAE
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END OF KEY TO FERN AND ALLIED FAMILIES
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