5.3: Mosses
- Page ID
- 35331
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Mosses, Phylum Bryophyta
Gametophyte Generation
Mosses produce only leafy gametophytes. You can differentiate them from leafy liverworts because the leaves are arranged in a spiral and usually have a midrib-like struture called a costa. Like the other two groups of bryophytes, simple pores on the gametophyte allow for gas exchange (no guard cells, meaning pores are permanently open).
![A group of moss gametophytes](https://bio.libretexts.org/@api/deki/files/26845/Moss_(Dicranum).jpg?revision=1&size=bestfit&width=511&height=383)
![Clustered green, leafy gametophytes. Thin leaves emerge at all angles from each gametophyte.](https://bio.libretexts.org/@api/deki/files/45317/1.jpg?revision=1&size=bestfit&width=652&height=490)
![A close up of part of a moss leaf.](https://bio.libretexts.org/@api/deki/files/45318/2.jpg?revision=1&size=bestfit&width=520)
![A cluster of moss gametophytes.](https://bio.libretexts.org/@api/deki/files/45319/3.jpg?revision=1&size=bestfit&width=656&height=616)
![Labeled long section of a Mnium antheridial head](https://bio.libretexts.org/@api/deki/files/29952/InkedMnium_Antheridial_Head_left_half_LI.jpg?revision=1&size=bestfit&width=608&height=456)
![Mnium male gametophyte, looking down at the splash cup](https://bio.libretexts.org/@api/deki/files/45320/4.jpg?revision=1&size=bestfit&width=611&height=458)
![Long section through a Mnium female gametophyte](https://bio.libretexts.org/@api/deki/files/29953/InkedMnium_Archegonial_Head_2_LI.jpg?revision=1&size=bestfit&width=637&height=480)
![Mnium female gametophyte, with no obvious structures visible](https://bio.libretexts.org/@api/deki/files/45321/5.jpg?revision=1&size=bestfit&width=630&height=700)
Sporophyte Generation
Moss sporophytes have a complex set of structures at the top of a seta. When the sporophyte emerges, it tears off a piece of the female gametophyte's archegonium, leaving a coating called the calyptra. Mosses have a capsule, where the sporangia are housed. This capsule has a lid-like structure called an operculum, which pops off when spores have matured. Depending on the moss, the sporophyte may have a peristome (teeth-like sheets of cells that aid in spore dispersal). True stomata are present for gas exchange.
![Moss sporophytes (with calyptras) emerging from gametophytes](https://bio.libretexts.org/@api/deki/files/26846/Bryophyta_sporophytes.jpg?revision=1&size=bestfit&width=746&height=739)
![A moss sporophyte with an operculum](https://bio.libretexts.org/@api/deki/files/26844/Buxbaumia.jpg?revision=1)
![Moss sporophytes without calyptras, showing the operculum of each](https://bio.libretexts.org/@api/deki/files/27319/Sporophytes_moss_w_operculum.jpg?revision=1&size=bestfit&width=523&height=595)
![A moss sporophyte that still has a calyptra covering the capsule](https://bio.libretexts.org/@api/deki/files/26842/Moss_sporangium_calyptra.jpg?revision=1)
![A moss sporophyte that no longer has a calyptra or an operculum](https://bio.libretexts.org/@api/deki/files/26843/Moss_sporangium_peristome.jpg?revision=1)
Mnium Life Cycle
![Moss life cycle diagram](https://bio.libretexts.org/@api/deki/files/29954/InkedMnium_Life_Cycle_Bryophyta_LI.jpg?revision=1)