''Phaeoceros laevis'', the smooth hornwort, is a species of hornwort of the genus '' Phaeoceros''. It is commonly found in areas where moisture is plentiful, such as moist soils in fields, the banks of streams and rivers or inundated beneath the surface of the rivers. It grows to a maximum height of about 5 millimetres and the plants are monoecious; the sex organs are visible on the dorsal surface. 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 ...

is nearly flat on the upper surface. It is of dark green and somewhat lustrous color, devoid of intercellular spaces. Its capsule is commonly to in length. The base is surrounded by a cylindrical sheath that often flares at the mouth. Spores are yellow with a granular-papillose surface. The elaters are yellowish, often branches, and varying in size and form. The slender green capsules, when produced in large numbers, resemble grass tufts. Mature spores are necessary for species determination. The

cytology Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living an ...

of ''P. laevis'' has been subject to considerable study. In 1909,

Lotsy Johannes Paulus Lotsy or Jan Paulus Lotsy (11 April 1867 – 17 November 1931) was a Dutch botanist, specializing in evolution and heredity. He promoted the idea of evolution being driven by hybridization. Career Lotsy was born into a wealthy ...

reported that the plant contained one chloroplast in each cell 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 ...

and two in each cell of the sporophyte. The sporophyte is likened to an elongated spindle. Research conducted by Lorbeer in 1924 revealed that two plastids are present in a cell when it is undergoing cell division, of which according to McAllister may vary in size. The

centrosomes In cell biology, the centrosome (Latin centrum 'center' + Greek sōma 'body') (archaically cytocentre) is an organelle that serves as the main microtubule organizing center (MTOC) of the animal cell, as well as a regulator of cell-cycle progres ...

of the species, much like ''

Marchantia polymorpha ''Marchantia polymorpha'' is a species of large thalloid liverwort in the class Marchantiopsida. ''M. polymorpha'' is highly variable in appearance and contains several subspecies. This species is dioicous, having separate male and female plants ...

'', are composed of two

centrioles In cell biology a centriole is a cylindrical organelle composed mainly of a protein called tubulin. Centrioles are found in most eukaryotic cells, but are not present in conifers (Pinophyta), flowering plants (angiosperms) and most fungi, and are ...

apposed end-to end, which are connected by a continuation of their cartwheel structures. Bryophyta 4

References

* {{Taxonbar, from=Q3490169 Hornworts Bryophyta of North America Flora of the United States Plants described in 1753 Taxa named by Carl Linnaeus