Fissidens bryoides
Fissidens arcticus
bryoid fissidens moss, lesser pocket-moss
arctic fissidens moss
unbranched and branched;
axillary hyaline nodules absent;
central strand usually present.
usually unbranched;
axillary hyaline nodules absent;
central strand weak.
as many as 20 pairs, lanceolate to oblong-lanceolate or oblong-lingulate, acute to short-acuminate or obtuse-apiculate, to 0.8–2.7 × 0.2–0.5 mm;
dorsal lamina narrowed proximally, ending at or before insertion, infrequently slightly decurrent;
vaginant laminae 1/2 leaf length, mostly equal;
margin entire but often serrulate distally, limbate on all laminae, limbidium reaching apex or ending a few cells before or partially absent to infrequently completely absent, limbidial cells 1–3-stratose;
costa excurrent to ending as many as 6 cells before apex, bryoides-type;
laminal cells 1-stratose, distinct, smooth, often slightly bulging, firm-walled, irregularly hexagonal, a few elongate, 6.5–16 µm, somewhat larger in proximal parts of vaginant laminae.
as many as 40 pairs, lanceolate to oblong-lanceolate, generally broadly acute, 0.4–1.5 × 0.2–0.3 mm;
dorsal laminae narrowed proximally, often ending well before insertion;
vaginant laminae 1/2–3/4 leaf length, ± equal, minor lamina ending on or near margin;
margin entire but often ± serrate distally, limbate on the vaginant laminae, infrequently limbate on dorsal and ventral laminae of perichaetial leaves, limbidial cells 1-stratose;
costa usually ending 2–3 cells before apex, bryoides-type;
laminal cells 1-stratose, distinct, smooth, slightly bulging, firm-walled, irregularly quadrate to hexagonal, 8–11 µm. Sexual condition polyoicous, most frequently gonioautoicous;
naked antheridia often in axils of distal leaves.
1.4–10 mm.
1.75–6 mm.
polyoicous;
naked antheridia and archegonia often in axils of distal leaves.
theca exserted, erect, radially symmetric to ± inclined, bilaterally symmetic, 0.2–1.2 mm;
peristome bryoides-type;
operculum 0.5 mm.
theca exserted, usually erect, radially symmetric, 0.4–0.8 mm;
peristome bryoides-type;
operculum 0.6 mm.
cucullate smooth, to 0.5 mm.
not seen.
10–20 µm.
14–20 µm.
1–2 per perichaetium.
1 per perichaetium.
Fissidens bryoides
Fissidens arcticus
Fissidens bryoides is a veritable kaleidoscope of intergrading expressions. At one extreme is F. bryoides in the strict sense, with plants gonioautoicous and the limbidium, 1–3 cells thick, confluent at the leaf apex with the percurrent to short-excurrent costa. At the other extreme is the expression that has been singled out as F. exiguus, with plants rhizautoicous and the 1-stratose limbidium usually restricted to the vaginant laminae of perichaetial leaves. In rare cases the limbidium can be absent from all leaves. All expressions, however, have clear, distinct, 1-stratose, irregularly hexagonal laminal cells, 6.5–16 µm, that in transverse section are no deeper than wide, and that have smooth walls that can be slightly bulging. H. A. Crum and L. E. Anderson (1981) illustrated the major expressions found in the flora area. Axillary, multicellular gemmae have been reported in Indian specimens.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Differing opinions have been expressed on the taxonomic standing of Fissidens arcticus. According to W. C. Steere (1978), it might be only an environmentally induced expression of F. bryoides, but A. A. Frisvoll (1981), who reported the species from Svalbard, suggested that it be treated as a subspecies or variety of F. bryoides. They and other previous workers (Steere and G. R. Brassard 1974; M. A. Bruggeman-Nannenga and E. Nyholm 1986), however, did not mention the dimorphic stems, of which the fertile (perichaetial) ones are shorter and have fewer pairs of leaves than the infertile ones. That character and the tendency of the limbidium to be expressed on all laminae of the leaves of perichaetial stems but otherwise restricted to the vaginant lamina of infertile stems distinguish F. arcticus.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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