''Megaceros'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of hornworts in the family

Dendrocerotaceae The Dendrocerotaceae is the only family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the wel ...

. The genus is found in the Old World tropics of east

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are ...

and Australia. Its name means 'big horn', and refers both to the exceptionally large size of the

gametophyte A gametophyte () is one of the two alternating multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the ...

thallus 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 ...

and to the large, horn-shaped sporophyte that the plants produce. Many

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

have a branching thallus that is more than two centimeters wide. The gametophytes are

monoicous Monoicy () is a sexual system in haploid plants (mainly bryophytes) where both sperm and eggs are produced on the same gametophyte, in contrast with dioicy, where each gametophyte produces only sperm or eggs but never both.Crandall-Stotler, B.J ...

. The genus ''Megaceros'' is unusual among hornworts in that the sporophyte does not have stomata, and the spores are green because they contain chloroplasts, as does the related genus ''

Dendroceros ''Dendroceros'' is a genus of hornworts in the family Dendrocerotaceae.Renzaglia, Karen S. & Kevin C. Vaughn. (2000) "Anatomy, development and classification of hornworts", pages 1-20 ''in'' A. Jonathan Shaw & Bernard Goffinet (Eds.), ''Bryophy ...

''. They can have as many as 14 chloroplasts per cell, the highest known number in hornworts.Bryophyte Biology
/ref> The

elater An elater is a cell (or structure attached to a cell) that is hygroscopic, and therefore will change shape in response to changes in moisture in the environment. Elaters come in a variety of forms, but are always associated with plant spores. In ...

s are

helical Helical may refer to: * Helix, the mathematical concept for the shape * Helical engine, a proposed spacecraft propulsion drive * Helical spring, a coilspring * Helical plc, a British property company, once a maker of steel bar stock * Helicoil A t ...

. The genus ''Megaceros'' was first recognized in 1907 by D. Campbell. More recently, the genera ''

Nothoceros ''Nothoceros'' is a genus of hornworts in the family Dendrocerotaceae. The genus is found in New Zealand, South America, and neotropical and eastern North America North America is a continent in the Northern Hemisphere and almost e ...

'' and '' Phaeomegaceros'' have been split off from this genus. The former genus includes all New World species previously included in ''Megaceros''.

References

* Parihar, N. S. (1961). ''An Introduction to Embryophyta, Volume I''. Allahbad: Central Book Depot.

External links

Megaceros in Australia

Name changes in Megaceros
{{Taxonbar, from=Q6808315 Hornworts Bryophyte genera