Porella is a large and widespread genus of liverworts belonging to the family Porellaceae within the order Porellales. Liverworts are non-vascular land plants (division Bryophyta sensu lato, or more precisely placed in Marchantiophyta), and Porella is one of the most species-rich and commonly encountered genera in this group. Depending on the taxonomic authority consulted, the genus encompasses between roughly 84 species (as recognised in 2016) and approximately 150 species accepted by GBIF, with most species concentrated in East Asia.
Members of Porella are recognisable by their characteristic leafy structure: each shoot bears leaves divided into a prominent large upper lobe and a distinctly smaller lower lobe (underleaf), giving the plants a layered, scale-like appearance when viewed from above. The plants typically grow as dense, flat mats or overlapping fronds on the bark of trees, making epiphytic bark colonisation their most characteristic habitat.
The genus has a cosmopolitan distribution across temperate regions of the world. It is particularly diverse in East Asia but is also well represented in Europe, North America, and other temperate zones. In North America, several species including Porella pinnata and Porella roellii are recorded from regions such as Montana.
Distribution
Porella has a wide cosmopolitan distribution centred on temperate regions. The genus is most diverse in East Asia, which holds the majority of its species. It also occurs across Europe, North America, and other temperate parts of the world, where plants grow characteristically on tree bark in moist, shaded environments.
Ecology
Species of Porella are predominantly epiphytes, growing attached to the bark of trees in temperate woodlands. The overlapping lobed leaves retain moisture and shade the substrate, and the genus is a frequent component of the bryophyte communities found on shaded, humid tree trunks.
Taxonomy Notes
Porella belongs to the order Porellales and the family Porellaceae within the class Jungermanniopsida (leafy liverworts). Species counts vary considerably by authority: approximately 84 species were recognised in 2016, while World Flora Online accepts 125 species and GBIF accepts around 150 species.
