Fissidens fontanus
Fissidens adianthoides
fissidens moss, water pocket moss
fissidens moss, maidenhair pocket-moss
usually profusely branched;
axillary hyaline nodules absent;
central strand absent.
mostly branched;
axillary hyaline nodules absent;
central strand present.
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.
as many as 60 pairs, somewhat undulate, oblong to lanceolate, acute, occasionally obtuse, to 3.5 × 1.2 mm;
dorsal lamina rounded or narrowed proximally, ending at insertion, not decurrent;
vaginant laminae 1/2–3/5 the leaf length, ± equal, minor lamina ending on or near margin;
margin crenulate to regularly serrulate but irregularly serrate distally, elimbate;
costa ending 2–3 cells before apex to percurrent, taxifolius-type;
laminal cells usually 1-stratose, infrequently and irregularly 2-stratose in the dorsal and ventral laminae, distinct, smooth, ± plane, firm-walled, irregularly quadrate to hexagonal, 10–20 µm, 1–5 marginal rows usually thinner with slightly thicker walls, forming a lighter marginal band, juxtacostal cells larger, mostly oblong and pellucid;
vaginant laminal cells somewhat larger.
0.5–0.6 mm.
to 25 mm.
gonioautoicous and cladautoicous;
perigonia and perichaetia on short axillary branches, 1–5 per leaf axil, sometimes on elongate, axillary branches.
dioicous (?);
perigonia not seen;
perichaetia on short axillary branches, generally confined to proximal half of stems.
theca 0.5–0.6 mm, erect, radially symmetric;
peristome anomalous, irregularly divided, ± incomplete, often truncate, papillose;
operculum as long as seta.
theca mostly ± inclined, ± arcuate, bilaterally symmetric, to 1.5 mm;
peristome taxifolius-type;
operculum to 1.5 mm.
mitrate, smooth.
cucullate, smooth, to 2.5 mm.
18–27 µm.
13–22 µm.
1–5 per leaf axil, inconspicuous.
1 per perichetium.
Fissidens fontanus
Fissidens adianthoides
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.)
The usually 1-stratose, distinct, smooth, plane laminal cells, lighter band of marginal laminal cells, and short perichaetial stems in the axils of proximal leaves distinguish Fissidens adianthoides. The species, nevertheless, can be confused with F. osmundioides, which has similar laminal cells without a marginal band of lighter cells and a serrate leaf apex, but which differs in having terminal perichaetia and papillose rhizoids. Fissidens dubius, which also has short perichaetial stems in the axils of proximal leaves and often a lighter band of marginal laminal cells, differs from F. adianthoides in its smaller and rather obscure laminal cells that are consistently irregularly 2-stratose. Fissidens adianthoides and F. dubius (as F. cristatus), according to cytological evidence presented by L. E. Anderson and V. S. Bryan (1956), are distantly related.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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