Sp. Musc. Frond., 298. 1801.
Plants small to large, glossy. Stems trailing; rhizoids on primary stems and at base of secondary stems, from clusters of initials abaxial to leaf insertions, not or sparsely and irregularly branched; axillary hairs 250–918 µm. Leaves closely or distantly spaced, ovate, oblong-ovate, oblong-lanceolate, ovate-lanceolate, lanceolate, narrowly lanceolate, or linear, keeled, conduplicate, concave, or plane; margins sometimes broadly reflexed proximally, plane, erect, or involute at apex, entire proximally, entire or serrulate at apex; apex acute, broadly acute, or obtuse; ecostate or nearly so; alar cells subrectangular to oblong, enlarged, bulging, walls lax; medial laminal cells linear-fusiform to long-rhomboidal. Perigonia lateral on short branches. Perichaetia with leaves oval, suboval, or suborbiculate, sheathing setae and capsule. Seta 0.1–0.3 mm. Capsule immersed to slightly emergent, ovoid to subcylindric; annulus rudimentary; operculum conic to obtuse-conic; endostome trellis perfect or imperfect. Calyptra mitrate, covering distal capsule. Spores 12–50 µm, sometimes of 2 sizes.
North America, South America, Eurasia, Africa, Atlantic Islands (Iceland).
Species 13 (10 in the flora).
Fontinalis is aquatic or semi-aquatic; many species occur in seasonally dry habitats, but all are submerged for at least part of the year. The genus exhibits remarkable gametophytic variability, not only between populations but also within single collections of Fontinalis. The greatest morphological variability is in species that are submerged part of the year.
Fontinalis has creeping stems or stolons adnate to the substrate and indeterminate in growth. Secondary stems are often sparsely, irregularly branched. The axillary hairs are remarkably long, to over 900 µm. The leaves have a multistratose basal region that has been interpreted as a rudimentary costa. The perichaetial leaves are usually lacerated across their apices. There are sporophytic character-complexes within Fontinalis that show meaningful taxonomic patterns at the species level; however, since the genus is dioicous, sporophytes are rare. Aquatic adaptations of sporophyte-associated features in Fontinalis include: perigonia with few antheridia (1, 2, or 4–6); enlarged, well-developed vaginula; immersed or emergent, very thick-walled capsules; lack of stomata; and peristomes with endostomial trellises.
The taxonomy of Fontinalis is complicated by the small number of useful gametophytic characters. In addition, because some important features are macroscopic, proper identification requires large, healthy collections.
|1||Stem leaves all or some keeled, conduplicate||> 2|
|1||All leaves concave or plane||> 6|
|2||Stems usually slender; leaves 2-4(-5) mm||> 3|
|2||Stems medium to robust; leaves 4-8 mm||> 4|
|3||Stem and branch apices flaccid, short-attenuate; medial laminal cells 100-150 × 12-18 µm; perichaetial leaf apices obtuse (gracilis expression).||Fontinalis antipyretica|
|3||Stem and branch apices stiff, long-attenuate; medial laminal cells 120-180 × 4-8 µm; perichaetial leaf apices apiculate to cuspidate.||Fontinalis neomexicana|
|4||Stem and branch leaves keeled, keels ± curved entire leaf length.||Fontinalis antipyretica|
|4||Stem leaves keeled or mostly keeled, keels ± straight beyond basal curve, branch leaves variously concave||> 5|
|5||Branch leaves concave, keeled; stem and branch apices sharply angled, swollen, flaccid (oreganensis expression).||Fontinalis antipyretica|
|5||Branch leaves concave or tubular-concave, not keeled; stem and branch apices not angled, firm, loosely foliate.||Fontinalis howellii|
|6||Leaf margins erect to incurved at apex or a mixture of erect and plane when moist||> 7|
|6||Leaf margins plane at apex when moist||> 11|
|7||Stems medium to robust; leaves flaccid or firm, concave or plane when moist||> 8|
|7||Stems slender; leaves firm, usually strongly concave when moist||> 9|
|8||Stem and branch apices swollen and loosely foliate or sometimes tightly short-attenuate; leaves firm, concave; margins erect to incurved at apex; medial laminal cells linear-fusiform, 80-180 µm.||Fontinalis novae-angliae|
|8||Stem and branch apices tightly long-attenuate; leaves usually flaccid, weakly concave, often some plane; margins erect-incurved or plane at apex; medial laminal cells long-rhomboidal, 60-120 µm (vernalis expression).||Fontinalis sphagnifolia|
|9||Branch leaves linear-lanceolate (aestivalis expression).||Fontinalis sphagnifolia|
|9||Branch leaves ovate-lanceolate to lanceolate or oblong-lanceolate||> 10|
|10||Leaves monomorphic; margins plane or occasionally erect at apex when moist, narrowly reflexed when dry; capsules immersed, ellipsoid to oval; perichaetial leaf apices acute or apiculate.||Fontinalis dalecarlica|
|10||Leaves weakly dimorphic or monomorphic; margins erect to incurved at apex when moist, not reflexed when dry; capsules emergent, cylindric to subcylindric; perichaetial leaf apices broadly rounded.||Fontinalis welchiana|
|11||Stem and branch apices short-attenuate or loosely foliate||> 12|
|11||Stem and branch apices tightly long-attenuate||> 14|
|12||Leaves monomorphic; stem leaves ovate, ovate-lanceolate, lanceolate, narrowly lanceolate, or linear-lanceolate.||Fontinalis hypnoides|
|12||Leaves strongly dimorphic; stem leaves narrowly lanceolate to linear||> 13|
|13||Stems rigid; stem leaves 6-9 mm; apices obtuse.||Fontinalis redfearnii|
|13||Stems flaccid; stem leaves 2-6(-9) mm; apices acute.||Fontinalis sullivantii|
|14||Leaves dimorphic; stem leaves narrowly lanceolate to linear.||Fontinalis sullivantii|
|14||Leaves monomorphic or dimorphic; stem leaves ovate-lanceolate, oblong-lanceolate, or lanceolate||> 15|
|15||Stems medium or robust; leaves flaccid, weakly concave or plane (vernalis expression).||Fontinalis sphagnifolia|
|15||Stems slender; leaves firm, strongly concave||> 16|
|16||Leaves ovate-lanceolate to lanceolate; margins usually reflexed proximally when dry.||Fontinalis dalecarlica|
|16||Leaves linear-lanceolate; margins not reflexed proximally when dry (aestivalis expression).||Fontinalis sphagnifolia|