page_title: Pogonatum urnigerum
section_title: Life cycle
hierarchical_section_title: Pogonatum urnigerum / Life cycle
context_page_description: Pogonatum urnigerum is a species of moss in the family Polytrichaceae, commonly called urn haircap. The name comes from "urna" meaning "urn" and "gerere" meaning "to bear" which is believed to be a reference made towards the plant's wide-mouthed capsule. It can be found on gravelly banks or similar habitats and can be identified by the blue tinge to the overall green colour. The stem of this moss is wine red and it has rhizoids that keep the moss anchored to substrates. It is an acrocarpous moss that grows vertically with an archegonium borne at the top of each fertilized female gametophyte shoot which develops an erect sporophyte.
context_section_description: Similar to other bryophytes, Pogonatum urnigerum completes its life cycle in two generations which is a cycle called the heteromorphic alternation of generations. It has a dominant gametophyte generation and a shorter sporophyte generation. After being dispersed as a haploid spore, it develops protonema. The first stage of protonema is chloronema which consists of irregular branching, transverse crosswalls, round chloroplasts, and no budding. After further development, the later stage of protonema, caulonema, develops. Caulonema is more regularly branched, has oblique crosswalls, has spindle-shaped chloroplasts and forms buds. Rhizoids also develop to help the gametophyte attach to its substrate. The caulonema buds eventually develop into a full gametophyte which undergoes mitosis to create reproductive sperm or egg (both are haploid, reproductive sperm are housed in an antheridium, an egg is housed in an archegonium). The gametophyte is unisexual and will produce either sperm or egg and not both at the same time. Sperm is transported, often by water, to an archegonium located on the top of a female gametophyte shoot. Once an egg has been fertilized, it develops a diploid sporophyte structure which is composed of a foot, seta, sporangium, and operculum. The foot supplies the developing sporangium with nutrients from the gametophyte. The seta elevates the sporangium. The sporangium develops within a hairy calyptra and produces spores through meiosis. Mature spores are dispersed through the openings of the sporangium's nematodontous teeth either by limited teeth movement or by wind. The small openings between the nematodontous teeth prevent all the spores from being dispersed at once which gives the sporophyte the advantage of dispersing spores over a longer period of time.
  Through its life cycle, Pogonatum urnigerum alternates between a haploid and diploid life cycle. The haploid structures include: the spores, the protonema, the rhizoids, the leaves, the reproductive structures, the calyptra (developed from an archegonium) and the stem of the gametophyte. Diploid structures include: the foot, the seta, the sporangium, and the operculum.
caption: Life cycle of moss.
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