Epiphytic, epiphyllic or rarely lithophytic or terrestrial, monoicous or dioicous. Asexual reproduction by caducous leaves (not in Victoria) or leaf fragments (not in Victoria), caducous short-leaved lateral branches (not in Victoria), or discoid gemmae produced on leaf margins or surfaces. Plants yellowish green to green, rarely brownish, irregularly and infrequently branched to regularly pinnate to tripinnately branched, with two ranks of lateral leaves and usually a third rank of underleaves, rarely underleaves absent, rarely a bipinnate thallus with leaves confined to reproductive branches (not in Victoria). Branches emerging from main stem near and ventral to an unmodified lateral leaf or rarely near a lateral leaf lacking lobule, with or rarely without a collar at base; collar when present usually lobed and leaf-like, rarely unlobed. Lateral leaves incubous, imbricate to distant, when moist horizontally spreading or erect from substrate, rarely convolute when dry, broadly attached to stem or narrowly attached to stem sometimes by only a single cell, with a main lobe, a smaller or occasionally larger abaxial lobule and sometimes a filamentous to linear stylus appendage abaxial to lobule in leaf axil (not in Victoria); main lobe not lobed, entire to dentate (not in Victoria), rounded or acute at apex, sometimes reduced to a flange bounded by an enlarged lobule; lobule directly attached to stem, sometimes reduced to a basal flange or a few cells in leaf axil, when well-formed usually saccate or inflated along basiscopic margin, often flattening toward apical margin, broadly attached to main lobe along basiscopic margin to form a keel, occasionally fused with lobe along all of margin except for a small opening facing stem covered by a lid, dentate with 1–9 teeth along acroscopic margin, with a hyaline papilla either on margin at base of tooth furthest from the stem on side facing stem (proximal marginal), on margin at base of tooth furthest from stem on side facing away from stem (distal marginal), or on internal face of cavity formed by the lobule usually near or on tooth furthest from stem (ental). Underleaves when present, smaller than lateral leaves, unlobed, emarginate or distinctly bilobed, entire or dentate (not in Victoria), one or two per lateral leaf pair; leaf cells mostly hexagonal or pentagonal, often becoming subquadrate near margin, smooth, mammillose or rarely papillose, thin- to thick-walled, often with intermediate thickenings, with or without distinct trigones, with 2–numerous oil bodies, rarely with ocelli cells composed of a single large oil body occupying most of the cell lumen and lack chloroplast near base or scattered throughout lobe (not in Victoria). Rhizoids in fascicles from underleaf bases or an equivalent position on stem when underleaves absent, without internal peg-like thickenings, hyaline or brown. Androecia terminal on main stem or lateral branches, of 2–numerous bracts, each covering 1–2 antheridia. Sporophyte terminal on branch or main stem, surrounded by a calyptra and perianth; perianth usually obovate or pyriform, occasionally cylindric (not in Victoria) or ellipsoid (not in Victoria), 3–5-keeled, with 2 keels (not in Victoria), with several keels, or sometimes not keeled (not in Victoria), usually beaked at apex. Seta short, barely elevating capsule beyond perianth. Capsule globose, bistratose, dehiscing by 4 valves; elaters present, uni- or rarely bispiral (not in Victoria). Spores globose to ellipsoid, bluntly papillose, with rosette markings scattered regularly over the surface, green, shed singly.

Widespread in moist tropical to temperate regions of the world with around 1800 species in around 73 genera (Heinrichs et al. 2013; Söderström et al. 2016; Gradstein et al. 2017; Ye & Zhu 2018; Zhu & Shu 2018a,b; Zhu et al. 2018, 2019; Renner & de Lange 2020); nine genera and 14 species in Victoria.

The largest family of liverworts defined by leaves with abaxial lobules that are fused along most of their length and the production of rhizoids from the abaxial stem at the base of the underleaves or in the position where this would be if underleaves were present. They are particularly diverse in tropical areas and form a large component of epiphyllous communities, exemplified by a report of a single leaf hosting 25 Lejeuneaceae species (Lücking 1997).

Gradstein, S.R., Zhu, R.-L., Shu, L. & Pérez, Á.J. (2017). Reinerantha foliicola, a new genus and species of Lejeuneaceae subtribe Cololejeuneinae (Marchantiophyta) from Ecuador. Journal of Systematics and Evolution 56: 67–75.

Heinrichs, J., Dong, S., Schäfer-Verwimp, A., Pócs, T., Feldberg, K., Czumaj, A., Schmidt, A.R., Reitner, J., Renner, M.A.M., Hentschel, J., Stech, M. & Schneider, H. (2013). A Molecular phylogeny of the leafy liverwort Lejeunea (Porellales): evidence for a Neotropical origin, uneven distribution of sexual systems and insufficient taxonomy. PLoS ONE 8(12): e82547.

Lücking, A. (1997). Diversity and distribution of epiphyllous bryophytes in a tropical rainforest in Costa Rica. Abstracta Botanica (Budapest) 21: 79–87.

Renner, M.A.M. & de Lange, P.J. (2020). A revised circumscription for Siphonolejeunea and a new species from New Zealand. Australian Systematic Botany 33: 311–326.

Söderström, L., Hagborg, A., von Konrat, M., Bartholomew-Began, S., Bell, D., Briscoe, L., Brown, E., Cargill, D.C., Costa, D.P., Crandall-Stotler, B.J., Cooper, E.D., Dauphin, G., Engel, J.J., Feldberg, K., Glenny, D., Gradstein, S.R., He, X., Heinrichs, J., Hentschel, J., Ilkiu-Borges, A.L., Katagiri, T., Konstantinova, N.A., Larraín, J., Long, D.G., Nebel, M., Pócs, T., Puche, F., Reiner-Drehwald, E., Renner, M.A.M., Sass-Gyarmati, A., Schäfer-Verwimp, A., Moragues, J.S., Stotler, R.E., Sukkharak, P., Thiers, B.M., Uribe, J., Váňa, J., Villarreal, J.C., Wigginton, M., Zhang, L. & Zhu, R. (2016). World checklist of hornworts and liverworts. Phytokeys 59: 1–828.

Ye, W. & Zhu, R.-L. (2018). Gaolejeunea, a new genus from China and new member of subtribe Echinolejeuneinae (Lejeuneaceae, Marchantiophyta). The Bryologist 121: 41–48.

Zhu, R.-L. & Shu, L. (2018). The systematic position of Microlejeunea ocellata (Marchantiophyta: Lejeuneaceae), an extraordinary species endemic to Australia and New Zealand. The Bryologist 121: 158–165.

Zhu, R.-L., Shu, L., Mustapeng, A.M.A., Q. & Suleiman, M. (2017). Thiersianthus (Marchantiophyta: Lejeuneaceae), a new genus from lowland rainforests in Borneo. The Bryologist 120: 511–520.

Zhu, R.-L., Shu, L., Bastos, C.J.P. & Bôas-Bastos, S.B.V. (2018a). Yanoella (Marchantiophyta: Lejeuneaceae), a new genus from the Brazilian Atlantic forest. The Bryologist 121: 264–274.

Zhu, R.-L., Shu, L., He, Q. & Wei, Y.-M. (2018b). Soella (Marchantiophyta: Lejeuneaceae), a new genus from China and Japan. The Bryologist 121: 324–339.

Zhu, R.-L., Bi, X.-F. & Shu, L. (2019). Mohamedia, a new genus of Lejeuneaceae (Marchantiophyta) from Oceania and tropical Asia. The Bryologist 122: 84–97.

Phalaris arundinacea