Leptodictyum riparium
Leptodictyum
knapwort, Kneiff's feathermoss, riparian trailing moss, streamside leptodictyum moss
leptodictyum moss
6–20 cm, flaccid, irregularly branched.
and branch leaves erect- to wide-spreading, not secund, oblong-lanceolate, not plicate, 2–6 mm;
base not decurrent;
margins plane, entire or obscurely serrulate, limbidia absent;
apex acuminate, acumen plane;
costa single, ending 3/5–3/4 leaf length;
alar cells differentiated or not, rectangular, enlarged, walls thin, region gradually delimited, not extending up leaf;
medial laminal cells linear, 42–117 µm;
marginal cells 1-stratose.
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.
autoicous.
brown to reddish, 2.2–2.5 mm;
annulus deciduous, 2- or 3-seriate, cells large;
operculum conic, apiculate;
peristome yellow to brown.
inclined to horizontal, cylindric, curved;
peristome perfect;
exostome teeth bordered;
endostome cilia 1–4, nodulose.
naked.
10–19 µm.
Leptodictyum riparium
Leptodictyum
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.)
Species 7 (2 in the flora).
L. Hedenäs (2003b) included in Leptodictyum only a single, variable species, L. riparium, with L. humile treated in Amblystegium. According to A. Vanderpoorten et al. (2001, 2002b), L. humile should be treated as a member of Hygroamblystegium. From a morphological point of view, there is a continuum between Hygroamblystegium humile and H. tenax, the only actual feature distinguishing the two being the length of the costa, which continuously varies from ceasing at mid leaf to percurrent. The most recent molecular analyses (Vanderpoorten, pers. comm.) suggest that L. riparium falls within a completely unrelated clade together with large Campylium species. Vanderpoorten et al. (2002b) suggested that L. riparium appears more closely related to Campyliadelphus chrysophyllus and Campylium stellatum than to species of Amblystegium. In Leptodictyum, the endostome segments are hyaline and filiform; the spores are minutely papillose.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Stems 6-20 cm, flaccid; basal laminal cell walls lax; alar regions differentiated. | L. riparium |
1. Stems 3-6 cm, stiff; basal laminal cell walls firm; alar regions not differentiated. | L. wallacei |
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