Belongs within: Pottiaceae.
Barbula is a genus of about 200 mosses found in temperate parts of the world. Members of the genus have axillary hairs that are almost always entirely composed of hyaline cells; leaves that are adaxially usually deeply grooved along the costa; distal laminal cell papillae that are rough, knobby, obscuring the lumens, and protuberant along the distal laminal margins; costae that are usually excurrent as a sharp mucro or an apiculus of one or more clear cells; and peristomes that are long and twisted (R. H. Zander). A number of species previously included in Barbula have been separated as the genus Didymodon. Notable species include B. unguiculata, common in eastern North America and Europe, with more or less obtuse leaves with plane margins and inconspicuous perichaetial leaves (Dixon 1924).
Characters (from R. H. Zander): Plants loosely cespitose or forming cushions, yellowish brown, brown or blackish distally, yellowish brown to reddish brown proximally. Stems short to elongate, to 2(-3.5) cm; hyalodermis rarely present, sclerodermis present, central strand present; axillary hairs short to elongate, all cells almost always hyaline. Leaves appressed incurved to weakly spreading, often contorted or twisted about stem, occasionally catenulate when dry, spreading when moist; ligulate or broadly lanceolate to long-triangular, adaxial surface usually deeply grooved along costa, occasionally broadly concave; base weakly differentiated to broadened and somewhat sheathing, proximal margins sometimes narrowly decurrent; margins usually recurved in proximal 1/2-2/3, occasionally plane throughout, entire or occasionally weakly denticulate near apex, lamina 1-stratose; apex rounded to obtusely acute, usually mucronate, occasionally entire or apiculate; costa percurrent to shortly excurrent as a sharp mucro, occasionally ending a few cells before the apex, adaxial outgrowths absent, adaxial cells elongate, occasionally quadrate to short-rectangular, in 2-3(-5) rows; transverse section ovate to semicircular, adaxial epidermis differentiated, adaxial stereid band usually present, usually small, guide cells 2-4 in 1 layer, hydroid strand occasionally present, abaxial stereid band present, usually strong, semi-lunar in sectional shape, abaxial epidermis usually present but weakly differentiated; proximal cells differentiated across leaf or reaching higher medially or occasionally marginally, rectangular, usually little wider than the distal cells, 3-5:1, walls of proximal cells thin to evenly thickened; distal medial cells quadrate, usually 1:1, 1-stratose; papillae hollow or solid, multiplex to 2-fid, 2-3 per lumen, occasionally simple or absent, cell walls thin to evenly thickened, superficially bulging on both free sides. Specialized asexual reproduction by tubers borne on proximal rhizoids or gemmae borne on axillary stalks. Sexual condition dioicous or possibly sometimes rhizautoicous. Perichaetia terminal, interior leaves sometimes strongly sheathing, little differentiated or ovate to long-lanceolate, laminal cells usually rhomboid in proximal 1/2-3/4. Seta 0.5-2.5 cm. Capsule stegocarpous, theca ovate to longly cylindric, annulus weakly differentiated to strong, of 1-3 rows of vesiculose cells, sometimes revoluble or deciduous in pieces; operculum usually long-conic; peristome teeth of 32 narrow rami, filamentous to narrowly triangular, usually strongly twisted counterclockwise. Calyptra cucullate. Spores mostly 8-12 µm. KOH laminal color reaction yellow, occasionally yellowish orange.
<==Barbula Hedw. 1801 (nom. cons.)SK02 |--B. (sect. Barbula) unguiculata Hedw. 1801OZB-O03, SK02 (see below for synonymy) `--B. sect. Convolutae (Bruch & Schimper) Schimper 1860 [=B. Untergruppe Convolutae Bruch & Schimper 1842]OZB-O03 |--B. convoluta Hedw. 1801OZB-O03, SK02 [=Streblotrichum convolutumOZB-O03; incl. B. convoluta var. densaOZB-O03] |--B. crocea (Brid.) Weber & Mohr 1807 [=Streblotrichum croceum; incl. B. paludosa]OZB-O03 `--B. enderesii Garov. 1840 [=Streblotrichum enderesii; incl. B. flavipes]OZB-O03 Barbula incertae sedis: B. acrophylla Müll.Hal. 1898SK02 B. alpigena [=Didymodon alpigenus]D24 B. ‘amoena’ Müll.Hal. 1898 (preoc.)SK02 B. andersoniiD03 B. antarcticaD03 B. arenaeD03 B. bescherelleiJ87 B. calycina Schwägr. 1823 (see below for synonymy)SK02 B. chrysopilaD03 B. conotrichaD03 |--B. c. var. conotrichaD03 `--B. c. var. fagicolaD03 B. consanguinea (Thwaites & Mitt.) Jaeger 1880SK02 B. constrictaN02 B. crinita Schultz 1823 (see below for synonymy)SK02 B. crispatulaD03 B. cylindrangia Müll.Hal. 1898SK02 B. densifoliaD03 B. ehrenbergii (Lorentz) Fleischer 1901SK02 B. eroso-denticulataN02 B. flagellarisD03 B. fuegianaD03 B. geminata Müll.Hal. 1901SK02 B. hampeana Paris 1894 [=B. brachyphylla (preoc.), Tortula brachyphylla]SK02 B. hastataN02 B. hispaniolensisJ87 B. ‘incerta’ Dixon 1941 (preoc.)SK02 B. indica (Hooker) Spreng. 1824SK02 B. inflexaB57 B. lechleriD03 B. luteola (Mitt.) Paris ex Catcheside 1980 [=Tortula luteola; incl. B. pungens, T. pungens (nom. illeg.)]SK02 B. patagonicaD03 B. perrubiginosa Dusén 1903D03 B. pseudo-ehrenbergiiBW15 B. pusillaD03 B. sardoa (Schimp.) Frahm 2004S04 (see below for synonymy) B. speirostega Müll.Hal. 1898SK02 B. subcalycina Müll.Hal. 1868 (see below for synonymy)SK02 B. subteretiusculaJ87 Nomina nuda: Barbula calycina var. attenuata Watts & Whitel. 1902SK02 Barbula commersonii Mitt. ex Muell. 1880 [=Tortula commersonii Paris 1906]SK02 Barbula flavido-pilosa Dusén 1903D03 Barbula microphylla Watts & Whitel. 1902SK02 Barbula micro-runcinata Dusén 1903D03 Barbula oedineura Müll.Hal. ex Watts & Whitelegge 1902 [=Tortula oedineura Watts & Whitel. 1902]SK02 Barbula pseudopilifera var. scabrinervis Broth. & Watts 1912SK02
Barbula calycina Schwägr. 1823 [=Tortella calycina, Tortula calycina; incl. Encalypta aristata, Pyramitrium aristatum, E. cristata (l. c.), Barbula aristatula, Tortula aristatula, B. calycina var. brevicaulis non B. fallax var. brevicaulis (n. n.), Tortula calycina var. brevicaulis (nom. inv.)]SK02
Barbula crinita Schultz 1823 [=Pseudocrossidium crinitum (Schultz) Zander 1993; incl. Tortula chlorotricha, Barbula chlorotricha (Broth. & Geh.) Paris 1894, T. flavinervis, B. pseudopilifera var. obscura (Dixon) Sainsbury 1952, Pseudocrossidium crinitum var. obscurum, T. flavinervis var. parviretes, T. hystrichosa (nom. inv.), Barbula pseudopilifera, T. pseudopilifera, B. tasmanica, T. tasmanica]SK02
Barbula sardoa (Schimp.) Frahm 2004S04 [=B. convoluta var. sardoaD24; incl. B. convoluta var. commutataS04, Trichostomum undatumD24]
Barbula subcalycina Müll.Hal. 1868 [=Tortula subcalycina; incl. B. angusticaulis Müll.Hal. 1902 (nom. inv.), Tortella angusticaulis Müll.Hal. ex Watts & Whitel. 1902 (n. n.), B. austrounguiculata Müll.Hal. 1901 (n. n.)]SK02
Barbula unguiculata Hedw. 1801OZB-O03, SK02 [=Bryum unguiculatumD24; incl. B. unguiculata f. apiculataOZB-O03, B. unguiculata var. cuspidataS04, B. unguiculata f. fastigiataOZB-O03, Tortula lanceolataOZB-O03, B. unguiculata f. microcarpaOZB-O03, B. unguiculata f. obtusifoliaOZB-O03]
*Type species of generic name indicated
References
[B57] Bartram, E. B. 1957. Additional Fijian mosses, III. Journal of the Washington Academy of Sciences 46 (12): 392–396.
[BW15] Brotherus, V. F., & W. W. Watts. 1915. The mosses of the New Hebrides [part 1]. Journal and Proceedings of the Royal Society of New South Wales 49 (1): 127–144.
[D24] Dixon, H. N. 1924. The Student’s Handbook of British Mosses 3rd ed. V. V. Sumfield: Eastbourne.
[D03] Dusén, P. 1903. Patagonian and Fuegian mosses. In: Scott, W. B. (ed.) Reports of the Princeton University Expeditions to Patagonia, 1896–1899 vol. 8. Botany pp. 63–126. The University: Princeton (New Jersey).
[J87] Judd, W. S. 1987. Floristic study of Morne La Visite and Pic Macaya National Parks, Haiti. Bulletin of the Florida State Museum—Biological Sciences 32 (1): 1–136.
[N02] Negi, H. R. 2002. Abundance and diversity of moss communities of Chopta-Tunganath in the Garhwal Himalaya. Journal of the Bombay Natural History Society 99 (3): 418–433.
[OZB-O03] Ochyra, R., J. Żarnowiec & H. Bednarek-Ochyra. 2003. Census Catalogue of Polish Mosses. Institute of Botany, Polish Academy of Sciences: Cracow.
[S04] Smith, A. J. E. 2004. The Moss Flora of Britain and Ireland 2nd ed. Cambridge University Press.
[SK02] Streimann, H., & N. Klazenga. 2002. Catalogue of Australian Mosses. Flora of Australia Supplementary Series 17. Australian Biological Resources Study: Canberra.