''Notothylas'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

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 la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Notothyladaceae The Notothyladaceae is the only family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the fa ...

. The genus is found globally, but is usually overlooked. It is the smallest of all the hornworts, with a yellow-green

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

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 wer ...

that is seldom more than a centimeter in diameter, and usually much smaller. The genus ''Notothylas'' is also unusual among hornworts in that the

sporophyte A sporophyte () is the diploid multicellular stage in the life cycle of a plant or alga which produces asexual spores. This stage alternates with a multicellular haploid gametophyte phase. Life cycle The sporophyte develops from the zygote pr ...

is bullet-shaped and does not grow very large (less than two millimeters). The sporophytes grow outwards rather than upwards, and like ''

Megaceros ''Megaceros'' is a genus of hornworts in the family Dendrocerotaceae. The genus is found in the Old World tropics of east Asia and Australia. Its name means 'big horn', and refers both to the exceptionally large size of the gametophyte thallu ...

'', there are no

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

ta on the surface of the sporophyte. 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 m ...

cells do not grow

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 ...

thickenings. Unlike many hornworts, species in ''Notothylas'' tolerate full sunlight.Module-Lower-Plants.pdf - Benson Idahosa University
/ref> A number of classification systems place ''Notothylas'' in its own order Notothyladales (frequently misspelled ''Notothylales'' in the literature). This classification is based on the assumption that the unique physical characteristics of the genus reflect an early divergence from other hornworts. However, this assumption is not supported by either phylogenetic analysis or fossil evidence. More recent classifications expand the definition of the family

to include four other genera.

References

* Asthana, A. K. & Srivastava, S. C. (1991). ''Indian Hornworts (A Taxonomic Study)''. J. Cramer: ''Bryophytorum Bibliotheca'', Band 42. . * Hässel de Menendez, G. G. (1988). A proposal for a new classification of the genera within the Anthocerotophyta. ''J. Hattori Bot. Lab.'' 64: 71-86. * Hicks, Marie L. (1992). ''Guide to the Liverworts of North Carolina''. Durham, NC: Duke University Press. . * Prihar, N. S. (1961). ''An Introduction to Embryophyta, Volume I''. Allahbad: Central Book Depot. * Singh, D. K. (2002) "Notothylaceae of India and Nepal(A Morpho-taxonomic revision). Bishen Singh Mahendra Pal Singh, Dehradun.

External links

{{Taxonbar, from=Q7063283 Hornworts Bryophyte genera