5.
Fissidens dubius
P. Beauvois, Prodr. Aethéogam. 57. 1805.
Fissidens adianthoides
var.
semicristatus
Grout;
F. cristatus
Mitten;
F. cristatus
var.
winonensis
(Renauld & Cardot) Grout;
F. decipiens
var.
winonensis
Renauld & Cardot;
F. floridanus
Lesquereux & James
Plants
to 25 × 3.5 mm.
Stem
usually branched; axillary hyaline nodules absent; central strand present.
Leaves
as many as 25 pairs, often undulate, oblong to lanceolate, obtuse to acute, often apiculate, to 3.5 × 0.7 mm; dorsal lamina truncate-rounded proximally, ending at insertion, not decurrent; vaginant laminae
2
/3 the leaf length, ± unequal, minor lamina ending near margin; margin crenulate to crenulate-serrulate but unevenly serrate at leaf apex, elimbate; costa ending a few cells before apex to percurrent, taxifolius-type; laminal cells irregularly 2-stratose in dorsal and ventral laminae, ± obscure, smooth, bulging, firm-walled, rounded-hexagonal, 7-10 µm, 3-4 rows of marginal cells thinner, walls slightly thicker, forming a pale marginal band.
Sexual condition
dioicous; perigonia on short axillary branches and elongate stems; perichaetia on short axillary branches, mostly near proximal ends of stems.
Sporophytes
1 per perchaetium.
Seta
to 11 mm.
Capsule
theca slightly inclined, slightly arcuate, bilaterally symmetric, to 1.8 mm; peristome taxifolius-type; operculum 1-1.4 mm.
Calyptra
cucullate, smooth, 1.8 mm.
Spores
13-20 µm.
Soil and humus, bases of trees, decaying wood, rocks and boulders in moist, shaded sites; N.B., Nfld. and Labr. (Nfld.), N.S., Ont., Que.; Ala., Alaska, Ariz., Ark., Calif., Conn., Del., Fla., Ga., Ill., Ind., Iowa, Kans., Ky., Maine, Mass., Mich., Minn., Miss., Mo., Neb., N.H., N.Y., N.C., Okla., Pa., S.C., Tenn., Tex., Vt., Va., W.Va., Wis.; Mexico; West Indies; Central America; Europe; Asia; Pacific Islands.
In contrast to
Fissidens adianthoides
,
F. dubius
has smaller, irregularly 2-stratose, obscure laminal cells. Subterranean, irregularly globose, multicellular rhizoidal gemmae have been reported for
F. dubius
as well as
F. osmundioides
and
F. taxifolius
in Europe and Japan. Z. Iwatsuki and T. Suzuki (1982) cited the occurrence of dwarf male plants (small perigonial stems located on the leaves of perichaetial plants) in Japanese specimens.
