Gemma (botany) in the context of "Alga"

Bryophytes (/ˈbraɪ.əˌfaɪts/) are a group of land plants (embryophytes), sometimes treated as a taxonomic division referred to as Bryophyta sensu lato, that contains three groups of non-vascular land plants: the liverworts, hornworts, and mosses. In the strict sense, the division Bryophyta consists of the mosses only. Bryophytes are characteristically limited in size and prefer moist habitats although some species can survive in drier environments. The bryophytes consist of about 20,000 plant species. Bryophytes produce enclosed reproductive structures (gametangia and sporangia), but they do not produce flowers or seeds. They reproduce sexually by spores and asexually by fragmentation or the production of gemmae.

Though bryophytes were considered a paraphyletic group in recent years, almost all of the most recent phylogenetic evidence supports the monophyly of this group, as originally classified by Wilhelm Schimper in 1879.

Marchantia is a genus of liverworts in the family Marchantiaceae and the order Marchantiales. The genus was named by French botanist Jean Marchant after his father. The widespread species Marchantia polymorpha has had its genome sequenced and is an incipient model organism.

The thallus of Marchantia shows differentiation into two layers: an upper photosynthetic layer with a well-defined upper epidermis with pores and a lower storage layer. The thallus features tiny cup-like structures called gemma cups, containing gemmae, small packets of tissue that are used for asexual reproduction. The combination of barrel-shaped pores and the circular shape of the gemma cups are diagnostic of the genus.