Weissia

Weissia controversa, photographed by Des Callaghan.

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. 1801 [incl. Hymenostomum Brown 1819] SK02
    |--W. subg. Eucladium D24
    |    |--W. curvirostris [=Barbula curvirostris, Gymnostomum curvirostre, Pottia curvirostris] D24
    |    |    |  i. s.: W. c. f. laeviuscula D24
    |    |    |--W. c. var. curvirostris D24
    |    |    |--W. c. var. cataractarum D24
    |    |    |--W. c. var. commutata [=Hymenostylium commutatum] D24
    |    |    |--W. c. var. insignis Dixon 1902 D24
    |    |    `--W. c. var. scabra [=Barbula curvirostris f. scabra] D24
    |    |--W. rupestris [=Gymnostomum rupestre; incl. Mollia aeruginosa, Barbula incavata] D24
    |    |--W. tenuis [=Gymnostomum tenue, Gyroweisia tenuis, Mollia tenuis] D24
    |    `--W. verticillata [=Bryum verticillatum, Eucladium verticillatum, Mollia verticillata] D24
    |--W. subg. Eu-Weisia D24
    |    |--W. brachycarpa (Nees & Hornsch.) Jur. 1882 D24, SK02 (see below for synonymy)
    |    |--W. controversa Hedw. 1801 D24, SK02 (see below for synonymy)
    |    |    |--W. c. var. controversa D24
    |    |    |--W. ‘viridula’ var. amblyodon [incl. W. viridula var. gymnostomoides] D24
    |    |    `--W. ‘viridula’ var. densifolia D24
    |    |--W. crispata [=Hymenostomum crispatum] D24
    |    |--‘Barbula’ exiguella Stirton 1897 D24
    |    |--W. microstoma (see below for synonymy) D24
    |    |    |--W. m. var. microstoma D24
    |    |    `--W. m. var. elata D24
    |    |--W. mucronata [incl. Mollia rutilans] D24
    |    |    |--W. m. var. mucronata D24
    |    |    `--W. m. var. subgymnostoma D24
    |    |--W. rostellata [=Hymenostomum rostellatum, Mollia rostellata, Phascum rostellatum] D24
    |    `--W. tortilis D24 (see below for synonymy)
    `--W. subg. Systegium D24
         |--W. crispa [=Phascum crispum, Mollia crispa, Systegium crispum] D24
         |    |--W. c. var. crispa D24
         |    `--W. c. var. aciculata D24
         |--W. levieri [=Astomum levieri] D24
         |--W. mittenii [=Astomum mittenii, Mollia mittenii, Systegium mittenii] D24
         |--W. multicapsularis (see below for synonymy) D24
         `--W. sterilis Nicholson 1903 D24

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’ castaneum J87
  W. edentula Mitt. 1859 [incl. W. pimpanae Müll.Hal. ex Kindb. 1889 (n. n.)] SK02
  W. fallax M08
  W. jamaicensis J87
  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 (see below for synonymy) SK02
  W. platystegia (Dixon) Eddy 1990 [=Astomum platystegium Dixon 1942] SK02
  W. rutilans (Hedw.) Lindb. 1863 [incl. W. muelleri (n. n.)] SK02
  ‘Hymenostomum’ sullivanii Müll.Hal. ex Geh. 1897 SK02
  W. triumphans M08
    |--W. t. var. triumphans M08
    `--W. t. var. pallidisetum M08
  W. willisiana (Sainsbury) Catches. 1980 [=Pottia willisiana] SK02
  W. wimmeriana D24

Nomina nuda: Hymenostomum amoenum Geh. ex Watts & Whitel. 1902 SK02
             Hymenostomum angustatum Broth. ex Watts & Whitel. 1902 SK02
             Hymenostomum pertortile Müll.Hal. ex Paris 1900 SK02
             Hymenostomum subolivaceum Müll.Hal. ex Watts & Whitel. 1902 SK02
             Weissia angustifolia Müll.Hal. ex Bailey 1890 SK02
             Weissia viridula f. eperistomata Hendey & Prent. 1970 SK02
             Weissia flavipes var. longifolia Broth. ex Watts & Whitel. 1902 SK02
             Weissia glauca Broth. ex Burges 1932 SK02
             Weissia graciliseta Broth. ex Bailey 1891 SK02
             Weissia perlinearis Müll.Hal. ex Bailey 1891 SK02
             Weissia squarrosa Broth. ex Bailey 1890 SK02 [=Hymenostomum squarrosum D24, Hyophila squarrosa Broth. ex Watts & Whitel. 1902 SK02, Mollia squarrosa D24]
             Weissia tenera Broth. ex Bailey 1891 [=Hyophila tenera Broth. ex Watts & Whitel. 1902] SK02

Weissia brachycarpa (Nees & Hornsch.) Jur. 1882 D24, SK02 [=Hymenostomum microstomum var. brachycarpum (Nees & Hornsch.) Huebener 1833 SK02, W. microstoma var. brachycarpa SK02]

Weissia controversa Hedw. 1801 D24, SK02 [incl. Weissia flavipes SK02, Hyophila inflexa SK02, Weissia nudiflora var. major Hampe 1856 (n. n.) SK02, Webera nudiflora var. major (n. n.) SK02, Weissia niflora SK02, Bryum nudiflorum SK02, Webera nudiflora (nom. inv.) SK02, Weissia riparia SK02, Dicranoweisia riparia SK02, Weissia tortelloides Broth. ex Watts & Whitel. 1902 SK02, Weissia truncata Müll.Hal. ex Watts & Whitel. 1902 (n. n.) SK02, Bryum viridulum D24, Mollia viridula D24, Weissia viridula (nom. illeg.) SK02, Weissia weymouthii (preoc.) SK02, Weissia whiteleggeana Müll.Hal. ex Watts & Whitel. 1902 (n. n.) SK02]

Weissia microstoma [=Gymnostomum microstomum, Hymenostomum microstomum, Mollia microstoma; incl. W. microstoma var. obliqua] D24

Weissia multicapsularis [=Phascum multicapsulare, Mollia multicapsularis, Systegium multicapsulare; 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 perpusilla (Müll.Hal.) Stone 1980 [=Phascum perpusillum, Astomum perpusillum, Hymenostomum perpusillum] SK02

Weissia tortilis D24 [=Gymnostomum tortile D24, Hymenostomum tortile (Schwägr.) Bruch & Schimp. 1846 SK02, Mollia tortilis D24; incl. Weissia condensa SK02]

*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.

[SK02] Streimann, H., & N. Klazenga. 2002. Catalogue of Australian Mosses. Flora of Australia Supplementary Series 17. Australian Biological Resources Study: Canberra.

Last updated: 18 December 2017.