Hygroamblystegium varium (Hedw.) Mönk.(Amblystegiaceae) is another moss frequently found in aquatic habitats in central Florida, along with
Leptodictyum,
Fontinalis, and species of
Fissidens. Its leaves are shorter and spread more 3-dimensionally around the stem than those in
Lepidodictyum, and the stems branch more frequently.
Fontinalis is easily distinguished from these genera as its leaves lack a midrib altogether. The leaf cells in
Fontinalis are also more elongate and curved, and the stalks of the sporangia (capsules) are extremely short.
Fissidens, of course, is easily recognized by the smaller secondary leaves attached at each node with the main leaves. Like
Amblystegium and
Leptodictyum, which are in the same family, the capsules of
Hygroamblystegium are erect, but slightly curved, and arise from short stems along the creeping main stems.
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Compared to the related genus, Leptodictyum, the stems branch more frequently in Hygroamblystegium, and the leaves
are shorter, more scale-like, and distributed 3-dimensionally around the stem. The capsule is upright, but slightly curved and asymmetric. From a dried specimen, Wagner-Merner s.n., 17 May 1969 (USF). |
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Leaf cells of Hygroamblystegium are short-rectangular or sometimes
more elongate. |
The family Amblystegiaceae is one of many moss families in taxonomic flux. Even the treatment in Flora North America (FNA) is self-proclaimed to be tentative, with the treatment of genera and species still controversial and unsettled.
Hygroamblystegium and
Amblystegium, each containing only one recognixed species, are weakly separated, and sometimes combined into a single genus. The principal differences noted in FNA are that the leaves of
Amblystegium are smaller than those of
Hygroamblystegium and the midrib is weaker, and that the plants lack paraphyllia (extra leaf-like or thread-like appendages between leaves).
Amblystegium is also said to be always terrestrial, while
Hygroamblystegium is often (but not always!) aquatic. By this definition it appears that
Amblystegium serpens is found only in north Florida, and reports from central Florida need to be investigated.
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A lucky shot of the tip of the capsule of Hygroamblystegium varium. |
In herbaria,
Hygroamblystegium varium is more likely to be filed under
Amblystegium, and it might be best to leave them there until the taxonomic dust settles. Some other species have been recognized, including
Hygroamblystegium tenax,
H. fluviatale,
H. humile,
H. trichopodium, and
H. noterophilum, but it seems clear that these are all just variants of the aptly named
H. varium.