Leptodictyum riparium
knapwort, Kneiff's feathermoss, riparian trailing moss, streamside leptodictyum moss
6–20 cm, flaccid, irregularly branched.
erect- to wide-spreading or appearing distichous, somewhat complanate especially in branches, often obliquely attached to stem, slightly contorted when dry, 2.5–6 mm;
margins entire;
apex broadly short- to gradually long-acuminate;
costa (45–)52–114 µm wide at base;
alar region differentiated;
basal laminal cell walls lax;
distal cells (34–)42–117 × 7–12(–13) µm. Seta single, light to dark brown, 0.8–2.6 cm.
brown to reddish, 2.2–2.5 mm;
annulus deciduous, 2- or 3-seriate, cells large;
operculum conic, apiculate;
peristome yellow to brown.
naked.
Leptodictyum riparium
As the specific epithet implies, Leptodictyum riparium occurs along rivers, often in flooded areas where the plants are stranded on tree bases in hardwood forests. The species is sometimes confused with another wetland species, Drepanocladus aduncus, which differs by its axillary hairs with 1–3 hyaline distal cells. There is tremendous morphological variability among the North American specimens of L. riparium, suggesting the existence of several ecotypes, which have been erroneously named as many varieties and forms in Leptodictyum, Amblystegium, and Campylium; these synonyms are summarized by A. J. Grout (1928–1940, vol. 3), H. S. Conard (1959), and H. A. Crum and L. E. Anderson (1981).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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