Fissidens fontanus
Fissidens hallianus
fissidens moss, water pocket moss
fissidens moss
usually profusely branched;
axillary hyaline nodules absent;
central strand absent.
usually profusely branched;
axillary hyaline nodules absent;
central strand absent.
in numerous pairs, lanceolate to linear-lanceolate, frequently somewhat falcate, acute, to 7 × 0.6 mm;
dorsal lamina narrowed proximally, usually ending before insertion;
vaginant laminae 1/3–1/2 the leaf length, unequal, minor lamina usually rounded and free distally or narrowed and ending on or near costa;
margin ± entire, elimbate;
costa ending 15–35 cells before apex, bryoides-type;
laminal cells usually 1-stratose, sometimes 2-stratose juxtacostally, quadrate to short-oblong to hexagonal, smooth, slightly bulging, ± firm-walled, 15–23 × 10–18 µm in dorsal and ventral laminae, juxtacostal cells largest.
in numerous pairs, lanceolate to linear-lanceolate, acute, to 6.5 × 0.7 mm;
dorsal lamina narrowed proximally, usually ending before insertion;
vaginant laminae 1/4–1/2 leaf length, acute, unequal in most leaves, minor lamina rounded above, attached on or near costa, ± equal on proximal part of stem, minor lamina ending near leaf margin;
margin ± entire, elimbate or limbate in the proximal 2/3 or less of vaginant laminae;
costa ending 5–15 cells before apex, bryoides-type;
laminal cells 1-stratose, distinct, smooth, slightly bulging, ± firm-walled, quadrate to oblong to hexagonal, 10–15 × 9–11 µm. Sexual condition cladautoicous;
perigonia on elongate, axillary branches;
perichaetia terminal on mains stems and elongate, axillary branches.
0.5–0.6 mm.
0.7–1.5 mm, often bent at the vaginula.
gonioautoicous and cladautoicous;
perigonia and perichaetia on short axillary branches, 1–5 per leaf axil, sometimes on elongate, axillary branches.
theca 0.5–0.6 mm, erect, radially symmetric;
peristome anomalous, irregularly divided, ± incomplete, often truncate, papillose;
operculum as long as seta.
theca erect, radially symmetric, 0.4–0.8 mm;
peristome anomalous, teeth variable, undivided and often fenestrate to divided 2/3 their length, even in same capsule, nearly smooth to papillose proximally, filaments with straight or spiral thickenings or striations;
operculum 0.4–0.6 mm.
mitrate, smooth.
not seen.
18–27 µm.
14–32 µm.
1–5 per leaf axil, inconspicuous.
1–2 per perichaetium.
Fissidens fontanus
Fissidens hallianus
Fissidens fontanus and F. hallianus are aquatic species usually found in stagnant or slow moving water, but at times emergent because of fluctuating water levels (H. A. Crum and L. E. Anderson 1981; P. G. Davison and D. E. Wujek 1999). Plants of both species are usually profusely branched, delicate, and feathery in appearance with leaves often 10 times or more as long as wide. Often plants are encrusted with diatoms. Stems and leaves might also appear black due to deposition of organic matter. When dry the leaves are unusually fragile so that when being prepared for herbarium storage it is best to float plants onto sheets prior to drying.
A suite of gametophytic and sporophytic characters distinguishes Fissidens fontanus. The unequal vaginant laminae are about 1/4–1/3 the leaf length, and minor lamina is round and more or less free distally. In addition, costa ends well below the leaf apex. In fertile specimens, the clusters of 1–5 axillary, inconspicuous, dark sporophytes in each perichaetium are distinctive. The sporophytes, more prevalent than thought, are caducous and are often found in the bottom of the herbarium packets. The short seta is equal in length to that of operculum, and peristome teeth are greatly reduced, often consisting of only the truncated, undivided basal parts.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Fissidens hallianus, named for Elihu Hall, has been confused with F. fontanus; they can be found growing together and both have similar vaginant laminae, although in F. hallianus there can be a weak limbidiuim on the proximal margin. Moreover, the costa is longer in F. hallianus than in F. fontanus. The sporophytes of F. hallianus are terminal, the number per perichaetium usually fewer than in F. fontanus, the seta is longer, relative to the length of the capsule, and the peristome teeth are complete. Sexual reproduction appears to be dependent on seasonal exposure.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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