XX. LEPTODON Mohr, Observ. Bot. 27. 1803, name conserved * [Greek leptos, delicate, and odon, tooth, alluding to the peristome]
Secondary stems [circinate when dry], densely bipinnately branched, with branch clusters separated by unbranched fertile stem intervals; [paraphyllia abundant], branched, not foliose; pseudoparaphyllia subfoliose, entire. Stem leaves appressed or erect when dry, spreading when moist, oval to oblong-elliptic, margins plane or recurved on one side proximally, entire; apex mostly obtuse, occasionally broadly acute; costa single, ending before leaf apex; cells thick-walled, smooth; median cells short, isodiametric; alar cells weakly differentiated. Branch leaves smaller, with similar features. Sexual condition dioicous. Perichaetial leaf tips squarrose, and perichaetia with with 2-seriate paraphyses. Seta short, to 1.5--2 mm. Capsule emergent, erect, ovoid to oblong-ellipsoid, stomata absent, annulus absent; operculum obliquely rostrate; peristome whitish, hydrocastique, teeth 16, spiculose, linear-lanceolate, united at the base, endostome rudimentary. Spores brownish yellow, minutely papillose, mostly 12--15 \um. Calyptra cucullate, hairy.
Species 4 (1 in the flora): temperate North America; South America (Chile); Eurasia; n, s, c Africa; Pacific Islands (New Zealand); e Australia.
A "double" sporophyte maturation cycle is present (that is, sporophyte maturation requires two winters, and thus two sporophyte cohorts mature simultaneously along the same stem), as with species of Forsstroemia, Alsia, Dendroalsia, and Neckera.
SELECTED REFERENCES Enroth, J. 1992. Corrections to Cryptoleptodon, Forstroemia and Leptodon (Leptodontaceae, Musci). J. Hattori Bot. Lab. 71: 75--82. Buck, W. R. 1980. Animadversions on Pterigynandrum with special commentary on Forsstroemia and Leptopterigynandrum. Bryologist 83: 451--465.
1. Leptodon smithii
Hypnum smithii Dickson ex Hedwig, Sp. Musc. Frond., 264. 1801
Secondary stems flagelliform or irregularly pinnately branched, not circinate. Stem and branch leaves ovate to oblong-elliptical, decurrent, apex broadly acute to obtuse and rounded, 0.5--1 x 0.3--0.7 mm; costa single and extending 50--70% of leaf length or costa short and double; median laminal cells 8--12 x 6--12 \um. Sexual condition dioicous. Inflorescences and sporophytes unknown from North American material. Sporophytes absent.
Epiphytic on rock; high elevations; Colo.; South America; Africa; Eurasia; Pacific Islands (New Zealand); Australia.
Leptodon smithii in
North America is known from a single locality in Jefferson County, Colorado,
collected by Nelson in 1971, and subsequently recollected in 1972 (Nelson
1973). The absence of inflorescences, weakly developed circinate stems,
infrequent and 1-seriate paraphyllia, decurrent leaves, and the broadly acute
leaf apices all lead one to question the assignment of the
Nelson, P. P. 1973. Leptodon smithii (Musci,
Neckeraceae), a genus new to