''Megaceros'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

and

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

. 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 se ...

thallus and to the large, horn-shaped

sporophyte A sporophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the biological life cycle, life cycles of plants and algae. It is a diploid multicellular organism which produces asexual Spo ...

that the plants produce. Many

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

have a branching thallus that is more than two centimeters wide. The gametophytes are monoicous. The genus ''Megaceros'' is unusual among hornworts in that the

does not have

stoma In botany, a stoma (: stomata, from Greek language, Greek ''στόμα'', "mouth"), also called a stomate (: stomates), is a pore found in the Epidermis (botany), epidermis of leaves, stems, and other organs, that controls the rate of gas exc ...

ta, and the

spore In biology, a spore is a unit of sexual reproduction, sexual (in fungi) or asexual reproduction that may be adapted for biological dispersal, dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores fo ...

s are green because they contain

chloroplast A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...

s, 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 elaters are helical. The genus ''Megaceros'' was first recognized in 1907 by D. Campbell. More recently, the genera '' Nothoceros'' 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''. Allahabad: Central Book Depot.

External links

Megaceros in Australia

Name changes in Megaceros
{{Anthocerotophyta Hornwort genera