''Polytrichum strictum'', commonly known as bog haircap moss or strict haircap, is an

evergreen In botany, an evergreen is a plant which has foliage that remains green and functional through more than one growing season. This also pertains to plants that retain their foliage only in warm climates, and contrasts with deciduous plants, which ...

and

perennial A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wide ...

species of

moss Mosses are small, non-vascular flowerless plants in the taxonomic division Bryophyta (, ) '' sensu stricto''. Bryophyta (''sensu lato'', Schimp. 1879) may also refer to the parent group bryophytes, which comprise liverworts, mosses, and hor ...

native to '' Sphagnum''

bog A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and muskeg; a ...

s and other moist habitats in temperate climates. It has a

circumboreal The Circumboreal Region in phytogeography is a floristic region within the Holarctic Kingdom in Eurasia and North America, as delineated by such geobotanists as Josias Braun-Blanquet and Armen Takhtajan. It is the largest floristic region in t ...

distribution, and is also found in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

and

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...

Description

Like other species in the

Polytrichaceae Polytrichaceae is a common family of mosses. Members of this family tend to be larger than other mosses with a thickened central stem and a rhizome. The leaves have a midrib that bears photosynthetic lamellae on the upper surface. Species in ...

, ''Polytrichum strictum'' has leaves with a single costa, vertical lamellae, a water-repelling

cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...

, and rhizoids that appear to facilitate external water movement in addition to anchoring the plant. Dense tufts of slender stems from 6–12 cm form 20–40 cm hummocks in

s and similar substrates. Leaves are narrowly lanceolate, appressed to the stem when dry and spreading to erect when moist. The reddish awn (formed by the slightly excurrent costa) and smooth, inrolled leaf margins separate ''P. strictum'' from other

Polytrichum ''Polytrichum'' is a genus of mosses — commonly called haircap moss or hair moss — which contains approximately 70 species that cover a cosmopolitan distribution. The genus ''Polytrichum'' has a number of closely related sporophytic character ...

species; only juniper haircap moss (''P. juniperinum)'' shares these attributes. ''P. strictum'', however, can be easily distinguished by the wooly-tomentose white rhizoids that extend up its stems (absent in '' P. juniperinum''), as well as its boggy habitat and predilection for organic soils (in contrast to the weedy nature and preference for mineral soils that characterize '' P. juniperinum'').

Distribution

''Polytrichum strictum'' is found throughout

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

, the northern half of the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

, Greenland, Iceland, the Faroe Islands, northern Europe and Asia, as well as Antarctica and the southern half of South America. It is characteristic of boggy peatland habitats dominated by '' Sphagnum'' mosses, but can also be found in wet heaths,

tundra In physical geography, tundra () is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. The term ''tundra'' comes through Russian (') from the Kildin Sámi word (') meaning "uplands", "treeless moun ...

sedge The Cyperaceae are a family of graminoid (grass-like), monocotyledonous flowering plants known as sedges. The family is large, with some 5,500 known species described in about 90 genera, the largest being the "true sedges" genus ''Carex'' wit ...

meadows, and peaty forests from low to high elevations; in warmer climates, it is largely confined to relict

s. Its microhabitat is at the top of peat hummocks, which it often helps to form.

Reproduction

''Polytrichum strictum'' is

dioicous Dioicy () is a sexual system where archegonia and antheridia are produced on separate gametophytes. It is one of the two main sexual systems in bryophytes. Both dioicous () and monoicous gametophytes produce gametes in gametangia by mitosis rathe ...

, with male and female reproductive structures produced separately by male and female gametophytes, which are

haploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...

(1n). As in other ''

'' species, the antheridia are borne terminally on male plants and swell and burst when mature, launching

sperm Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, whi ...

into the air; in addition, they develop in splash cups, which further facilitate sperm dispersal by catching and harnessing the energy of rain drops. The lucky few sperm to land near the

archegonia An archegonium (pl: archegonia), from the ancient Greek ''ἀρχή'' ("beginning") and ''γόνος'' ("offspring"), is a multicellular structure or organ of the gametophyte phase of certain plants, producing and containing the ovum or female ga ...

of a female plant (also borne terminally) use their two whiplash

flagella A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

to swim down the neck and into the venter, where one will fertilize the

ovum The egg cell, or ovum (plural ova), is the female reproductive cell, or gamete, in most anisogamous organisms (organisms that reproduce sexually with a larger, female gamete and a smaller, male one). The term is used when the female gamete is ...

. Once

fertilisation Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Proce ...

takes place, the

zygote A zygote (, ) is a eukaryotic cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individual organism. In multicellula ...

develops into the

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respectively ...

(2n)

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 ...

, which consists of a foot (embedded in the tissue of the gametophyte), a seta (or stalk), and a capsule. The capsule, which is covered by a dirty-white calyptra, matures after the seta elongates, at which point the calyptra is shed. Within the capsule, each sporoctye undergoes

meiosis Meiosis (; , since it is a reductional division) is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells. It involves two rounds of division that ultimately resu ...

to produce four haploid (1n)

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, f ...

s; when these are mature, the operculum is projected and the spores are released through the peristome, which is joined by the epiphragm and ringed by 64 nematodontous teeth. When the proper conditions and substrate are available, the spores germinate into a filamentous protonema, from which the gametophytes emerge, completing the cycle.

Use in restoration

''Polytrichum strictum'' is considered an important pioneer species in peatlands, able to tolerate a wide range of environmental conditions and disturbance regimes. It is instrumental in preventing frost heaving in harvested peatlands, and research suggests it can be used in the restoration of unstable peat areas, although little is known about whether it aids or hinders ''Sphagnum'' growth.

References

{{Taxonbar, from=Q637826 Polytrichaceae Flora of Tasmania