''Anthoceros'' 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 ...

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 in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Anthocerotaceae The Anthocerotaceae is the only family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social o ...

. It is distributed globally. Species of ''Anthoceros'' are characterized by having a small to medium-sized, green

thallus Thallus (: 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. A thallus usually names the entir ...

that is more or less lobed along the margins.

Etymology

The name ''Anthoceros'' means 'flower horn', referring to the characteristic 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 ...

s that all hornworts produce.

Description

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 dark gray, dark brown or black. This distinguishes it from the related genus ''

Phaeoceros ''Phaeoceros'' is a genus of hornworts in the family Notothyladaceae. The genus is global in its distribution. Its name means 'yellow horn', and refers to the characteristic yellow spores that the plants produce in the horn-shaped sporophyte. T ...

'', which produces yellow spores. The

lacks air chambers and scales, and has no well defined mid rib. It has unicellular smooth rhizoids in the ventral region. It is irregularly lobed, and exhibits rare dichotomous branching. The thallus has little to no tissue differentiation, being composed of thin, compactly arranged uniform

parenchyma upright=1.6, Lung parenchyma showing damage due to large subpleural bullae. Parenchyma () is the bulk of functional substance in an animal organ such as the brain or lungs, or a structure such as a tumour. In zoology, it is the tissue that ...

tous cells. ''Anthoceros'' species are host to species of ''

Nostoc ''Nostoc'', also known as star jelly, troll's butter, spit of moon, fallen star, witch's butter (not to be confused with the fungi commonly known as witches' butter), and witch's jelly, is the most common genus of cyanobacteria found in a variety ...

'', a symbiotic relationship in which ''Nostoc'' provides nitrogen to its host through cells known as

heterocysts Heterocysts or heterocytes are specialized nitrogen-fixing cells formed during nitrogen starvation by some filamentous cyanobacteria, such as ''Nostoc'', ''Cylindrospermum'', and '' Anabaena''. They fix nitrogen from dinitrogen (N2) in the air ...

, and which are able to carry out

photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...

. The ''Nostoc'' colonies are present on the lower ventral surface. They often grow in slime pores, mucilaginous groups of decomposed cells within the plant which open outward through a pore guarded by 2 cells. ''Nostoc'' colonies are visible as blue-green patches on the plant body. The plants grow in moist clay soils on hills, in ditches, and in damp hollows among rocks.

Reproduction

''Anthoceros'' species exhibit many forms of asexual reproduction. Besides fragmentation, a nearly ubiquitous form, these hornworts exhibit tubers, persistent apices, and apospory. Tubers and persistent apices can remain dormant and survive harsh conditions to form new thalli. Apospory, a form of apomixis, involves the formation of diploid

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 ...

spores directly from the tissue of the plant's

Species

List of species. * '' A. adscendens'' Lehmann & Lindenberg 1832 * '' A. agrestis'' Paton 1979 * '' A. alpinus'' Stephani 1923 * '' A. angustifolius'' Gottsche, Lindenberg & Nees 1846 * '' A. angustus'' Stephani 1916 * '' A. assamicus'' Kachroo 1954 * '' A. bharadwajii'' Udar & Asthana 1985 * '' A. buettneri'' Stephani 1916 * '' A. capricornii'' Cargill & Scott 1997 * '' A. caucasicus'' Stephani 1923 * '' A. cavernosus'' Stephani 1916 non Nees 1838 * '' A. chambensis'' Kashyap 1917 * '' A. chungii'' Khanna 1938 * '' A. crispatus'' Griffith 1849 * '' A. cristatus'' Stephani 1916 * '' A. dimorphus'' Sim 1926 * '' A. dissectus'' Montagne 1846 * '' A. erectus'' Kashyap 1915 non Stephani 1916 * '' A. expansus'' (Stephani 1916b) Villarreal & Cargill 2015 * '' A. ferdinandi-muelleri'' Stephani 1916 * '' A. fragilis'' Stephani 1916 * '' A. fusiformis'' Austin 1875 * '' A. gasongorii'' Gola 1914 * '' A. granulatus'' Gottsche 1863 non Colenso 1886 * '' A. harrisanus'' (Stephani 1916b) Parihar 1962 * '' A. helmsii'' Stephani 1893 * '' A. jamesonii'' Taylor ex Mitten 1855 * '' A. javanicoides'' Miller 1981 * '' A. jungermannioides'' Schweinitz 1821 * '' A. kajumas'' (Goebel 1928) Proskauer 1951 * '' A. khandalensis'' (Apte & Sane 1942) Proskauer 1951 * '' A. koshii'' Khanna 1936 * '' A. lamellatus'' Stephani 1916 * '' A. laminiferus'' Stephani 1893 * '' A. macounii'' Howe 1898 * '' A. macrosporus'' Stephani 1916 * '' A. major'' Griffith 1849 non Micheli 1729 ex Schmidel 1766 non Smith 1806 * '' A. maritimus'' Stephani 1916b * '' A. megasporus'' Meijer 1957 * '' A. muscoides'' Colenso 1884 * '' A. myriandroecius'' Stephani 1911 * '' A. natalensis'' Stephani 1913 * '' A. neesii'' Proskauer 1958 * '' A. niger'' Stephani 1916 * '' A. orizabensis'' (Stephani 1916) Hässel 1990 * '' A. pandei'' Udar & Asthana 1985a * '' A. patagonicus'' Hässel 1990 * '' A. peruvianus'' Stephani 1916 * '' A. pinnatus'' Stephani 1886 * '' A. punctatus'' von Linné 1753 * '' A. pusillus'' Colenso 1886b non Stephani 1916 * '' A. rosulans'' Hasegawa 1986 * '' A. sahaydrensis'' Sane 1942 * '' A. sambesianus'' Stephani 1916 * '' A. sampalocensis'' (Burgeff 1935) Proskauer 1948 * '' A. scariosus'' Austin 1869 * '' A. schroederi'' Stephani 1912 * '' A. serratus'' Stephani 1911b * '' A. simulans'' Howe 1934 * '' A. spongiosus'' Stephani 1916 * '' A. stephanianus'' (Stephani 1916) Beauverd ex Stephani 1924 * '' A. subtilis'' Stephani 1916 * '' A. telaganus'' Stephani 1916 * '' A. tristanianus'' Villarreal, Engel & Váňa 2013Ibarra-Morales, A., M. E. Muñíz, and S. Valencia. (2015)
The genus ''Anthoceros'' (Anthocerotaceae, Anthocerotophyta) in Central Mexico.
''Phytotaxa'' .l. v. 205, n. 4, p. 215–28.'' * '' A. tuberculatus'' Lehmann & Lindenberg 1832 * '' A. venosus'' Lindenberg & Gottsche 1846 non Spruce 1885

References

{{Authority control Hornwort genera Taxa named by Carl Linnaeus