''Phaeoceros laevis'', the smooth hornwort, is a species of

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 ...

of the 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. ...

''. 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 Monoecy (; adj. monoecious ) is a sexual system in seed plants where separate male and female cones or flowers are present on the same plant. It is a monomorphic sexual system alongside gynomonoecy, andromonoecy and trimonoecy. Monoecy is conne ...

; the sex organs are visible on the dorsal surface. The thallus 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 of ''P. laevis'' has been subject to considerable study. In 1909, Lotsy reported that the plant contained one chloroplast in each cell of the gametophyte and two in each cell of 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 ...

. 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 of the species, much like '' Marchantia polymorpha'', are composed of two centrioles 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