Links to genera Ferns and Horsetails (Monilophytes) Clubmosses and Quillworts (Lycophytes)
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| Azolla | Aquatic, floating; rhizome fine, repeatedly branched, with submerged roots hanging down; tiny scale-like leaves alternate, overlapping, in two rows; leaves with two lobes, the upper thick and fleshy, the lower thin, colourless and submerged; sori (rarely seen) round, whitish, borne on lower surface of first leaf of branch.
About seven species, distributed worldwide. The one species found in Britain and Ireland is an introduction from North America.
* indicates introduced species.
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