3. Fontinalis Hedwig, Sp. Musc. Frond. 298. 1801. • [Latin, of a spring, alluding to aquatic habitat].
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.
Species 13 (10 in the flora): North America, South America, Eurasia, Africa, Atlantic Islands (Iceland).
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.
SELECTED REFERENCES Allen, B. H. 1983. On the costa of Fontinalis (Musci). Lindbergia 9: 37-40. Allen, B. H. 1986-2008. Fontinalaceae Exsiccatae. 6 fasc. in 174 nos. St. Louis. Allen, B. H. 1988. Studies on the genus Fontinalis (Musci: Fontinalaceae). Brittonia 40: 180-187.