Fissidens grandifrons
Fissidens arcticus
largeleaf fissidens moss
arctic fissidens moss
usually profusely branched;
axillary hyaline nodules present;
central strand absent.
usually unbranched;
axillary hyaline nodules absent;
central strand weak.
in as many as 60 or more pairs, lanceolate, obtuse to rounded, to 3 × 0.5 mm;
dorsal lamina narrowed proximally, ending at insertion;
vaginant laminae 1/2–2/3 leaf length, acute, equal;
margin ± entire to crenulate, elimbate;
costa usually difficult to discern, ending a few cells before apex, variable in structure, basically taxifolius-type;
lamina cells 1- to 4-stratose at leaf margin, 2- to pluristratose in interior of dorsal and ventral laminae, 1- to 4-stratose in vaginant laminae, smooth, ± plain, quadrate to hexagonal, 7–13 µm long.
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.
13–19 mm.
1.75–6 mm.
dioicous (?);
perigonia not seen;
perichaetia on short axillary branches in medial leaves.
theca slightly arcuate, bilaterally symmetric, astomatose, exothecial cells quadrate to oblong, vertical walls thicker than horizontal walls, 1.5–2 mm;
peristome taxifolius-type.
theca exserted, usually erect, radially symmetric, 0.4–0.8 mm;
peristome bryoides-type;
operculum 0.6 mm.
not seen.
20–23 µm.
14–20 µm.
1 per perichaetium.
Fissidens grandifrons
Fissidens arcticus
Fissidens grandifrons is the only species in the flora area with pluristratose laminal cells. It is a robust aquatic species, usually coarse to the touch. The plants are often brown-black, the result of deposition of organic matter. Reproduction in North America, where sporophytes have never been found, is by vegetative means. According to E. J. Hill (1902), multiplication is by small, radiculose branches that are easily detached in the rapidly running streams. Although the gametophyte of F. grandifrons is specialized to an aquatic habitat (thick, lanceolate leaves and long archegonia; Z. Iwatsuki and T. Suzuki 1982; R. A. Pursell and B. H. Allen 1994), the species has retained a distinctly terrestrial type of sporophyte. The description of the sporophyte given here is based on three specimens: Lai 8699 (NY) and Lin 12831 (NICH) from Taiwan; and Higuchi 20161 (NICH) from Pakistan. A. J. Grout (1943) stated that the operculum is “conic-rostrate, about 1 mm long,” and Iwatsuki and Suzuki reported that the calyptra is “cucullate, about 1.6 mm long, smooth.”
(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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