''Petalophyllum'', or petalwort, is a genus of liverworts in the

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Fossombroniales Fossombroniales is an order of liverwort The Marchantiophyta () are a division of non-vascular land plants commonly referred to as hepatics or liverworts. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which c ...

.Crandall-Stotler, B.J., Stotler, R.E., and Long, D.G. 2009. Phylogeny and classification of the Marchantiophyta. Edinburgh Journal of Botany, vo. 66, no. 1, p. 155-198. The plants are small, reaching lengths of up to about 15 mm (0.6 in), and

thallose Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms were ...

; that is, the plant is not differentiated into root, stem, and leaf. The thallus consists of a midrib flanked by two wings that bear leaf-like lamellae on their dorsal surface. The ventral surface bears rhizoids and two rows of small scales. ''Petalophyllum'' is

dioicous Dioicy () is a sexual system where archegonia and antheridia are produced on separate gametophytes. It is one of the two main sexual systems in bryophytes. Both dioicous () and monoicous gametophytes produce gametes in gametangia by mitosis rathe ...

. The gametangia are individually subtended by extensions of the dorsal lamellae. Antheridia occur in rows or clusters near the apex of the thallus.

Archegonia An archegonium (pl: archegonia), from the ancient Greek ''ἀρχή'' ("beginning") and ''γόνος'' ("offspring"), is a multicellular structure or organ of the gametophyte phase of certain plants, producing and containing the ovum or female ga ...

are clustered and surrounded by a pesudoperianth. Asexual reproduction occurs via apical tubers.

Species

''Petalophyllum'' lives primarily in seasonally dry habitats on disturbed soils and sand dunes in

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

, western Europe, northern Africa, India, New Zealand, and Western Australia. There are currently five recognized species: *'' Petalophyllum americanum'' is endemic to the

Gulf Coast of the United States The Gulf Coast of the United States, also known as the Gulf South, is the coastline along the Southern United States where they meet the Gulf of Mexico. The coastal states that have a shoreline on the Gulf of Mexico are Texas, Louisiana, Mississ ...

in Arkansas, Louisiana, Mississippi, and Texas. It was first described as the European species ''P. ralfsii'' in 1919,Evans, A.W. 1919. Notes on North American Hepaticae - VIII. Bryologist, vol. 22, p. 54-73. but a detailed study later showed that the North American form is a distinct species.Ford, C.H. and Crandall-Stotler, B.J. 2002. Contributions toward a monograph of ''Petalophyllum'' ( Marchantiophyta). Novon, vol. 12, p. 334-337. *''

Petalophyllum hodgsoniae ''Petalophyllum'', or petalwort, is a genus of liverworts in the order Fossombroniales.Crandall-Stotler, B.J., Stotler, R.E., and Long, D.G. 2009. Phylogeny and classification of the Marchantiophyta. Edinburgh Journal of Botany, vo. 66, no. 1, p ...

'' is known only from the

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * Ty ...

specimen, which was collected at Hawke's Bay on the North Island of New Zealand in 1947. It is considered threatened and possibly extinct.Glenny, D., Fife, A.J., Brownsey, P.J., Renner, M.A., Braggins, J.E., Beever, J.E. and Hitchmough, R. 2011. Threatened and uncommon bryophytes of New Zealand (2010 Revision). New Zealand Journal of Botany, vol. 49, no. 2, p. 305-327.De Lange, P.J., Glenny, D., Braggins, J.E., Renner, M., von Konrat, M., Engel, J.J., Reeb, C. and Rolfe, J.R. 2015. Conservation status of New Zealand

hornwort Hornworts are a group of non-vascular Embryophytes (land plants) constituting the division Anthocerotophyta (). The common name refers to the elongated horn-like structure, which is the sporophyte. As in mosses and liverworts, hornworts have a ...

s and liverworts, 2014. Publishing Team, Department of Conservation. *'' Petalophyllum indicum'' is found in the Punjab area of the Indian subcontinent. *'' Petalophyllum preissii'' is known from the Swan River are of Western Australia and from the North Island of New Zealand. *'' Petalophyllum ralfsii'' is found in the northern Mediterranean region as far east as Turkey, and along the Atlantic coast of Europe as far as northwest Scotland.Rumsey, F.J., Vogel, J.C. and Russell, S.J. 2001. A study of genetic variation in the threatened hepatic ''Petalophyllum ralfsii'' (Wils.) Nees and Gottsche (Fossombroniaceae). Conservation Genetics, vol. 2, no. 3, p. 271-277.

References

{{Taxonbar, from=Q17280863 Fossombroniales Liverwort genera