The bryophytes are those embryophyte plants ('land plants') that are non-vascular: they have tissues and enclosed reproductive systems, but they lack vascular tissue that circulates liquids. They neither flower nor produce seeds, reproducing via spores.
Modern studies of the land plants generally show one of two patterns. In one of these patterns, the liverworts were the first to diverge, followed by the hornworts, while the mosses are the closest living relatives of the polysporangiates (which include the vascular plants). In the other pattern, the hornworts were the first to diverge, followed by the vascular plants, while the mosses are the closest living relatives of the liverworts. Originally the three groups were brought together as the three classes of division Bryophyta. However, since the three groups of bryophytes form a paraphyletic group, they now are placed in three separate divisions.
These plants are generally gametophyte-oriented; that is, the normal plant is the haploid gametophyte, with the only diploid structure being the sporangium in season. As a result, bryophyte sexuality is very different from that of other plants. There are two basic categories of sexuality in bryophytes:
- Dioicous bryophytes produce only antheridia (male organs) or archegonia (female organs) on a single plant body.
- Monoicous bryophytes produce both antheridia and archegonia on the same plant body.
Some bryophyte species may be either monoicous or dioicous depending on environmental conditions. Other species grow exclusively with one type of sexuality.
- Marchantiophyta (liverworts)
- Anthocerotophyta (hornworts)
- Bryophyta (mosses)
- Plant sexuality
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