Fissidens taxifolius
Fissidens exilis
fissidens moss, yew-leaf pocket moss
fissidens moss, pygmy pocket moss, slender pocket-moss
mostly branched;
axillary hyaline nodules absent;
central strand present.
unbranched;
axillary hyaline nodules absent;
central strand absent.
as many as 15 pairs, often undulate, oblong to lanceolate, obtuse to broadly acute, cuspidate, to 2.7 mm × 0.6 mm;
dorsal lamina truncate-rounded proximally, ending at insertion, not decurrent;
vaginant laminae 2/3 the leaf length, ± equal, minor lamina ending on or near margin;
margin evenly serrulate, often crenulate-serrulate on dorsal and ventral laminae, elimbate;
costa ending in cuspidate apex, taxifolius-type;
laminal cells 1-stratose, distinct, smooth, bulging, firm-walled, irregularly hexagonal, 8–11 µm frequently paler at margin, conspicuously mammillose in vaginant laminae, larger and clearer juxtacostally.
as many as 4 pairs, lanceolate to oblong-lanceolate, acute to obtuse-apiculate, to 2.1 × 0.4 mm;
dorsal lamina ending before insertion;
vaginant laminae 2/5 leaf length, unequal, minor lamina narrowed, ending on or near costa;
margin of dorsal and ventral laminae ± entire to crenate-serrulate, crenate-dentate on vaginant laminae, elimbate;
costa percurrent to ending 2–3 cells before apex, bryoides-type;
laminal cells distinct, smooth, plane, firm-walled, irregularly quadrate to irregularly hexagonal, 10–15 µm, marginal cells slightly smaller, vaginant laminal cells somewhat larger with 2–3 intralaminal rows irregularly elongate.
to 17 mm.
2–9 mm.
rhizautoicous;
perigonia on short branches proximal to elongate stems;
perichaetia on short, proximal, axillary branches.
rhizautoicous;
perigonia gemmiform, proximal to perichaetial stems or scattered over protonemata.
theca slightly inclined, slightly arcuate, bilaterally symmetric, to 1.5 mm;
peristome taxifolius-type;
operculum to 1 mm.
theca exserted, erect, radially symmetric, infrequently slightly arcuate, bilaterally symmetric, to 0.7 mm;
operculum 0.4–0.6 mm;
peristome scariosus-type.
cucullate, smooth, to 2 mm.
cucullate, smooth, 0.5 mm.
13–18 µm.
11–14 µm.
1 per perichaetium.
1 per perichaetium.
Fissidens taxifolius
Fissidens exilis
Fissidens taxifolius is distinguished by evenly serrulate or crenulate-serrulate leaf margin, stout costa ending in leaf cusp, conspicuous mammillose cells in the vaginant laminae, and sporophytes on short branches in the axils of proximal leaves. It can be confused with F. bushii, but that species is smaller, has costa shorter, and cells in the vaginant laminae have small, more or less inconspicuous papillae in the corners of the walls. Fissidens taxifolius usually occurs on shaded, damp soil or humus, whereas F. bushii is usually found on disturbed soil in woods, along paths, and in road cuts. Fissidens clebschii is considered to be a freakish expression of F. taxifolius (R. A. Pursell 2003).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Fissidens exilis, first reported for North America by W. C. Steere (1950), is probably inadvertently introduced from Europe. It can be distinguished from all other tiny Fissidens in the flora area by the 2–3 rows of irregularly elongate intralaminal cells in the vaginant laminae. Plants of this species would be easily passed over were it not for the persistent protonemata that often form dark green velvetlike carpets over the substrate and the numerous sporophytes that are produced. The gemmiform perigonia are often seen scattered over the protonemata. B. H. Allen et al. (2004) have reviewed and mapped the distribution of F. exilis in North America.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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