Belongs within: Pottiaceae.
Weissia is a cosmopolitan genus of mostly soil-growing mosses. Most species of Weissia have sharply inflexed distal leaf margins, with a tendency to show adaxially bulging cells in leaf section; however, distinctions between Weissia and related genera such as Trichostomum are not always straightforward (R. H. Zander). In members of the subgenus Systegium, capsules are immersed and cleistocarpous; in members of Eu-Weisia and Eucladium, capsules are exserted and usually have a deciduous cap (Dixon 1924).
Characters (from R. H. Zander): Plants in low cushions or turfs or loosely caespitose, green above, brown to tan or yellow below. Stems to 1 cm, hyalodermis weakly differentiated to distinct, seldom absent, sclerodermis weakly differentiated in 1-2 layers, central strand present; axillary hairs with proximal 1-2 cells somewhat thicker walled. Leaves incurved, commonly tubulose and often contorted or spiraled when dry, spreading when moist; long-ligulate, oblong or triangular to long-lanceolate, 1.5-2.5(-4) mm; adaxial surface broadly channeled across leaf; base scarcely differentiated to ovate or rectangular, occasionally half-sheathing; distal margins usually sharply incurved, occasionally merely erect, seldom plane, entire; apex sharply acute to subulate, occasionally broadly acute, obtuse, or weakly cucullate; costa shortly and sharply mucronate, adaxial outgrowths absent, adaxial cells quadrate to short-rectangular except occasionally elongate near apex, in 4-8 rows; transverse section ovate, occasionally circular or semicircular, adaxial epidermis present, adaxial stereid band present, guide cells 4-6(-8) in 1 layer, hydroid strand absent, abaxial stereid band present, crescent in sectional shape, abaxial epidermis present or occasionally absent; basal cells differentiated across leaf, rarely rising higher along margins in a V, rectangular, occasionally rhomboid, 2-5:1; distal medial cells subquadrate to hexagonal, 7-13 μm, papillae 2-fid, 2-6 per lumen, occasionally fused into a large multiplex papilla covering the lumen, occasionally spiculiform and branching. Specialized asexual reproduction rare, as rhizoidal gemmae. Sexual condition monoicous (usually autoicous), occasionally dioicous; perichaetia terminal, interior leaves occasionally sheathing seta, little different from cauline leaves or somewhat larger. Seta 0.1-1.3 cm. Capsule stegocarpic or cleistocarpic; theca elliptical to short-ovate or cylindric, 1-2.2 mm, annulus in ca. 2 rows of persistent, vesiculose cells or not differentiated; operculum when present conic to rostrate; peristome teeth 16 or rudimentary or absent, occasionally removed with operculum, oblong-truncate to long-triangular, often irregularly cleft, straight or twisted weakly counterclockwise, mouth occasionally closed by a remnant of the spore sac. Calyptra cucullate. Spores 14-28 μm. KOH laminal color reaction yellow.
<==Weissia Hedw. 1801SK02 |--W. sect. WeissiaS04 | |--W. controversa Hedw. 1801D24, SK02 (see below for synonymy) | | |--W. c. var. controversaD24 | | |--W. c. var. crispataS04 (see below for synonymy) | | |--W. c. var. densifolia (Bruch & Schimp.) Wilson 1855S04 [=W. viridula var. densifoliaD24] | | `--W. c. var. wimmeriana (Sendtn.) Blockeel & Sm. 1998S04 [=Gymnostomum wimmerianumOZB-O03] | |--‘Barbula’ exiguella Stirton 1897D24 | |--W. perssonii Kindb. 1898 [=W. controversa var. perssonii]S04 | `--W. rutilans (Hedw.) Lindb. 1863S04 (see below for synonymy) | |--W. r. var. rutilansD24 | `--W. ‘mucronata’ var. subgymnostomaD24 |--W. sect. Astomum (Hampe) Nyholm 1989S04 [=Astomum Hampe 1837SK02, W. subg. Astomum (Hampe) Kindberg ex Saito 1975OZB-O03] | |--W. levieri (Limpr.) Kindb. 1897 [=Astomum levieri]S04 | |--W. × mitteniiS04 [=Astomum mitteniiS04, Mollia mitteniiD24, Systegium mitteniiD24] | |--W. longifolia Mitt. 1851S04 [=W. flavipes var. longifolia Broth. ex Watts & Whitel. 1902SK02] | | |--W. l. var. longifoliaS04 (see below for synonymy) | | `--W. l. var. angustifolia (Baumgartner) Crundw. & Nyholm 1972S04 [=W. angustifolia Müll.Hal. ex Bailey 1890SK02] | |--W. multicapsularis (Sm.) Mitt. 1851S04 (see below for synonymy) | |--W. rostellata (Brid.) Lindb. 1864S04 (see below for synonymy) | `--W. sterilis Nicholson 1903 [=Astomum crispum var. sterilis]S04 `--W. sect. Hymenostomum (Brit.) Müll. Hal. 1849S04 (see below for synonymy) |--W. brachycarpa (Nees & Hornsch.) Jur. 1882S04 (see below for synonymy) | |--W. b. var. brachycarpaS04 | |--W. ‘microstoma’ var. elataD24 | `--W. b. var. obliqua (Nees & Hornsch.) Hill 1981S04 [=W. microstoma var. obliquaD24] |--W. condensa (Voit) Lindb. 1863S04 (see below for synonymy) `--W. squarrosa (Nees & Hornsch.) Müll. Hal. 1849S04 (see below for synonymy) Weissia incertae sedis: W. alianuda Tan 1992 [incl. Pottia nuda Mitt. ex Muell. 1880 (n. n.), W. nuda Mitt. 1882 (preoc.)]SK02 W. balansae (Müll.Hal.) Zander 1993 [=Phasconica balansae Müll.Hal. 1882]SK02 ‘Hymenostomum’ castaneumJ87 W. edentula Mitt. 1859 [incl. W. pimpanae Müll.Hal. ex Kindb. 1889 (n. n.)]SK02 W. jamaicensisJ87 W. novae-valesiae (Broth. ex Roth) Stone 1980 [=Astomum novae-valesiae]SK02 ‘Hymenostomum’ olivaceum Müll.Hal. ex Geh. 1897 [incl. H. robustum]SK02 W. patula (Knight) Fife 1995 (see below for synonymy)SK02 W. perpusilla (Müll.Hal.) Stone 1980 [=Phascum perpusillum, Astomum perpusillum, Hymenostomum perpusillum]SK02 W. platystegia (Dixon) Eddy 1990 [=Astomum platystegium Dixon 1942]SK02 ‘Hymenostomum’ sullivanii Müll.Hal. ex Geh. 1897SK02 W. triumphansM08 |--W. t. var. triumphansM08 `--W. t. var. pallidisetumM08 W. willisiana (Sainsbury) Catches. 1980 [=Pottia willisiana]SK02 Nomina nuda: Hymenostomum amoenum Geh. ex Watts & Whitel. 1902SK02 Hymenostomum angustatum Broth. ex Watts & Whitel. 1902SK02 Hymenostomum pertortile Müll.Hal. ex Paris 1900SK02 Hymenostomum subolivaceum Müll.Hal. ex Watts & Whitel. 1902SK02 Weissia viridula f. eperistomata Hendey & Prent. 1970SK02 Weissia glauca Broth. ex Burges 1932SK02 Weissia graciliseta Broth. ex Bailey 1891SK02 Weissia perlinearis Müll.Hal. ex Bailey 1891SK02 Weissia tenera Broth. ex Bailey 1891 [=Hyophila tenera Broth. ex Watts & Whitel. 1902]SK02
Weissia sect. Hymenostomum (Brit.) Müll. Hal. 1849S04 [=Hymenostomum Brown 1819SK02, W. subg. Hymenostomum (Brown) Kindberg ex Saito 1975OZB-O03]
Weissia brachycarpa (Nees & Hornsch.) Jur. 1882S04 [=Hymenostomum microstomum var. brachycarpum (Nees & Hornsch.) Huebener 1833SK02, W. microstoma var. brachycarpaSK02; incl. W. ludwigiiS04, Gymnostomum microstomumD24, Hymenostomum microstomumS04, Mollia microstomaD24, Weissia microstomaS04, Hymenostomum microstomum var. obliquumOZB-O03]
Weissia condensa (Voit) Lindb. 1863S04 [=Gymnostomum condensumOZB-O03; incl. G. tortileD24, Hymenostomum tortile (Schwägr.) Bruch & Schimp. 1846SK02, Mollia tortilisD24, Weissia tortilisS04]
Weissia controversa Hedw. 1801D24, SK02 [=Grimmia controversaOZB-O03; incl. Wei. viridula var. amblyodonOZB-O03, Wei. viridula var. arenicolaOZB-O03, Wei. flavipesSK02, Wei. viridula var. gymnostomoidesD24, Hyophila inflexaSK02, Wei. nudiflora var. major Hampe 1856 (n. n.)SK02, Webera nudiflora var. major (n. n.)SK02, Wei. nifloraSK02, Bryum nudiflorumSK02, Webera nudiflora (nom. inv.)SK02, Weissia ripariaSK02, Dicranoweisia ripariaSK02, Wei. viridula var. stenocarpaOZB-O03, Wei. viridula var. subglobosaOZB-O03, Wei. tortelloides Broth. ex Watts & Whitel. 1902SK02, Wei. truncata Müll.Hal. ex Watts & Whitel. 1902 (n. n.)SK02, Bryum viridulumD24, Mollia viridulaD24, Weissia viridula (nom. illeg.)SK02, Wei. weymouthii (preoc.)SK02, Wei. whiteleggeana Müll.Hal. ex Watts & Whitel. 1902 (n. n.)SK02]
Weissia controversa var. crispataS04 [=Hymenostomum crispatumD24; incl. W. fallax Schlm. 1818OZB-O03, W. controversa var. fallaxS04, W. tortilis var. fallaxOZB-O03]
Weissia longifolia Mitt. 1851 var. longifoliaS04 [incl. W. crispa var. aciculataS04, Astomum crispumS04, Mollia crispaD24, Phascum crispumD24, Systegium crispumD24, Weissia crispaS04]
Weissia multicapsularis (Sm.) Mitt. 1851S04 [=Astomum multicapsularisS04, Mollia multicapsularisD24, Phascum multicapsulareD24, Systegium multicapsulareD24; incl. Phascum sphaericarpon (nom. inv.)D24]
Weissia patula (Knight) Fife 1995 [incl. W. viridula var. gymnostoma, W. controversa var. gymnostoma (Dixon) Sainsbury 1955, Gymnostomum inflexum, Hymenostomum inflexum Hampe & Müll.Hal. 1880 (n. n.), Pottia inflexa, Weissia inflexa]SK02
Weissia rostellata (Brid.) Lindb. 1864S04 [=Astomum rostellatumS04, Gymnostomum rostellatumOZB-O03, Hymenostomum rostellatumD24, Mollia rostellataD24, Phascum rostellatumD24]
Weissia rutilans (Hedw.) Lindb. 1863S04 [=Mollia rutilansD24; incl. W. viridula var. mucronataOZB-O03, W. muelleri (n. n.)SK02]
Weissia squarrosa (Nees & Hornsch.) Müll. Hal. 1849S04 [=Gymnostomum squarrosumOZB-O03, Hymenostomum squarrosumD24, Hyophila squarrosa Broth. ex Watts & Whitel. 1902SK02, Mollia squarrosaD24]
*Type species of generic name indicated
References
[D24] Dixon, H. N. 1924. The Student’s Handbook of British Mosses 3rd ed. V. V. Sumfield: Eastbourne.
[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.
[M08] Marstaller, R. 2008. Moosgesellschaften am Südrand des Kyffhäusergebirges bei Bad Frankenhausen (Kyffhäuserkreis). 130. Beitrag zur Moosvegetation Thüringens. Mauritiana 20 (2): 289–348.
[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.