Greek di, two, and trichos, hair-like; the peristome is split longitudinally into two segments

Rodney D. Seppelt, Robert R. Ireland and Harold Robinson

Plants small to moderately robust, in loose to dense tufts, green to yellowish green distally, yellow-brown to brown proximally. Stems erect, short or reaching 2 cm or more, simple or sometimes with a few branches; rhizoids smooth, at base of stems. Leaves erect-spreading, rigid to flexuose or sometimes somewhat falcate, small to elongate, lanceolate to subulate from a more or less sheathing base; margins entire throughout or denticulate near the apex; costa single, 1/6--1/3 width of leaf base, percurrent or excurrent, occupying most of subula, with a single row of guide cells, and both adaxial and abaxial bands, or adaxial stereid band sometimes weak or rarely absent or; distal lamina cells quadrate to short-rectangular, becoming longer and thinner walled proximally toward margins, smooth or rarely papillose at both ends. Specialized asexual reproduction by rhizoidal tubers in some species. Sexual condition monoicous or dioicous; perichaetial leaves usually with a longer and more or less sheathing base and shorter subulate than stem leaves. Seta solitary, pale yellow to dark reddish brown, slender, long-exserted, erect or flexuose. Capsule mostly erect and symmetric, ovoid to cylindric, sometimes arcuate or ± inclined, smooth; annulus present, mostly large, deciduous; operculum conic to short-rostrate; peristome single, the 16 teeth split into 2 filiform segments or sometimes irregularly perforate or split, with or without a short basal membrane, papillose to spiculose, straight or ± twisted when dry. Calyptra cucullate. Spores rounded, 6--25 µm, very finely papillose and appearing smooth, but minutely to coarsely verrucose, or with somewhat vermicular ornamentation, yellow to brown.

Species ca. 90 worldwide (11 in flora). Known from all continents, including the maritime Antarctic region; occurring from near sea level to montane regions, on a wide range of soils, occasionally on rock; some species calciphilic.

SELECTED REFERENCES

Allen, B. 1994. Moss Flora of Central America. Part 1. Sphagnaceae-Calymperaceae. Missouri Botanical Garden. Britton, E. G. 1913. Ditrichaceae. North American Flora 15(1): 55--67. New York. Crum, H. A. and L. E. Anderson. 1981. Mosses of Eastern North America. Vol.1. New York. Grout, A. J. 1936. Moss Flora of North America north of Mexico. Vol. 1, Part 1. Newfane. Ireland, R. R. 1982. Moss Flora of the Maritime Provinces, Publications in Botany 13, National Museums of Canada. Ottawa. Lawton, E. 1971. Moss Flora of the Pacific Northwest. Hattori Botanical Laboratory. Nichinan. Nyholm, E. 1986. Illustrated Flora of Nordic Mosses. Fasc. 1. Fissidentaceae-Seligeriaceae. Stockholm.

OTHER REFERENCES

Anderson, L. E. & V. S. Bryan. 1958. Systematics of the autoicous species of Ditrichum subg. Ditrichum. Brittonia 10: 121--137.
Best, G. N. 1893. Two new American mosses. Bull. Torrey Bot. Club 20: 116--117.
Bowers, F. D. & S. K.Freckmann. 1979. Atlas of Wisconsin bryophytes. Rep. Fauna Flora Wisconsin 16. 135 pp.
Corley, M. F. V., A. C. Crundwell, R. Düll, M. O. Hill, & A. J. E. Smith. 1981. Mosses of Europe and the Azores; an annotated list of species with synonyms from recent literature. J. Bryol. 11: 609--689.
Deguchi, H. & T. Matsui. 1986. Rhizoidal tubers of Ditrichum heteromallum in Japanese population. Proc. Bryol. Soc. Japan 4: 87.
Frisvoll, A. A. 1985. Lectotypifications including nomenclatural and taxonomic notes on Ditrichum flexicaule sensu lato. Bryologist 88: 31--40.
Grout, A. J. 1927. Studies in Ditrichum. Bryologist 30: 4--5.
Ireland, R. R. & H. Robinson. 2001. Taxonomic status of Ditrichum ambiguum and D. tortuloides. J. Hattori Bot. Lab. 91: 277--287.
Leiberg, J. B. 1893. Two new species of mosses from Idaho. Bull. Torrey Bot. Club 20: 112--116.
Matsui, T., H. Deguchi & R. D. Seppelt. 1985. Ditrichum lineare (Sw.) Lindb., with tubers in Asia. J. Jap. Bot. 60(2): 33--39.
Matsui, T. & Z. Iwatsuki. 1990. A taxonomic revision of the family Ditrichaceae (Musci) of Japan, Korea and Taiwan. J. Hattori Bot. Lab. 68: 317--366.
Novotny, I. 1996 (1997). Variability and distribution of Ditrichum flexicaule sensu lato in the Czech and Slovak Republics. Acta Mus. Moraviae, Sci. Nat. 81: 157--192.
Risse, S. 1985. Rhizoidal tubers on Ditrichum heteromallum (Hedw.) Britt. J. Bryol. 13: 527--531.
Robinson, H. 1966. New or little known mosses from the eastern United States. Bryologist 69: 105--109.
Seppelt, R. D. 1982. A monographic revision of the genus Ditrichum (Musci: Ditrichaceae). I. Australian and New Zealand species. J. Hattori Bot. Lab. 51: 99--150.