Hypnum

Hypnum is a genus of mosses belonging to the family Hypnaceae.[1]

Hypnum
Scientific classification Edit this classification
Kingdom: Plantae
Division: Bryophyta
Class: Bryopsida
Subclass: Bryidae
Order: Hypnales
Family: Hypnaceae
Genus: Hypnum

The genus has cosmopolitan distribution.[1] A common name sometimes used for Hypnum moss is "carpet moss".[2]

Distribution

Hypnum species are found on all continents except for Antarctica.[3] Species are typically found in temperate regions.[3]

Habitat

Hypnum species are typically found in moist forest areas on rotting logs, while some species are aquatic.[2][4] Species can also be found living on soil, rocks, and live trees.[4]

Identification

Identifying moss species in the field to the genus Hypnum by using a hand lens is considered quite feasible since most Hypnum species share common features with one another.[3] A very useful defining characteristic of Hypnum mosses are their leaves which are often falcate-secund (meaning that they are sickle-shaped and point to one side of the plant).[3] Another distinguishing characteristic of Hypnum mosses is the thick, green mats that they form, which earns them the common name "carpet moss".[2] Distinguishing between different Hypnum species can be accomplished mainly by gametophytic features and sometimes by sporophytic features.[3]

Description

General form

Gametophytes range from small to large in size.[3] Gametophytes are green, yellowish, or brown in colour, with the colouration appearing dull or glossy.[3] Gametophytes can sometimes form tufts.[3] Growth forms of Hypnum mosses vary from creeping to erect.[5]

Stem and branching patterns

Stems have pseudoparaphyllia.[3] Branching patterns include nearly unbranched, irregularly branched, or 1- or 2- times pinnate.[5][3]

Leaves

Branch leaves and stem leaves have similar shapes.[5] Leaves are secund or falcate-secund, broadly to narrowly ovate, and can be plicate.[3] Leaf bases can sometimes be decurrent.[3] Sometimes leaf margins are toothed on the distal region.[3] Leaf margins can be recurved proximally and are usually flat (i.e., not recurved) at the distal edge.[3] Leaf margins can sometimes be sinuate at the proximal region.[3] Leaf apices are either acute or acuminate.[3]

Despite having similar shapes, branch leaves are smaller than stem leaves.[5]

Leaves have a double costa or an obscure costa that spans 1/4 of the leaf's length.[3] Laminal cells are exclusively smooth.[3] Alar cells in the leaf bases are typically differentiated and range in shape from hexagonal, triangular, quadrate, or sub-quadrate.[3]

The outer perichaetial leaves are bent while the inner perichaetial leaves are erect.[3] In terms of shape, perichaetial leaves can be ovate, lanceolate, or subulate.[3] Apices of perichaetial leaves are acuminate.[3]

Calyptra

Calyptra are exclusively naked and have no hair.[3]

Seta

Setae are long and range in colour from yellowish to reddish.[5][3]

Sporangium

Orientation of the sporangium can be erect, inclined, or horizontal.[5][3] Sporangium shape varies from cylindrical to ovoid.[5] The sporangium is also typically curved.[3] There tends to be a contraction below the sporangium opening.[3] All species have two rows of peristome teeth.[3] The outer surface of exostome teeth have zigzag lines as well as lamellae.[3] The annulus is either 1-3- times seriate or has very minimal amounts of cell differentiation.[3] The operculum is conical to round in shape.[3]

Spores produced by the sporangium are round and can be smooth or papillose in texture.[3]

Reproduction

In terms of sexual reproduction, Hypnum mosses are autoicous, dioicous, or phyllodioicous.[3] Hypnum mosses do not have any specialized forms of asexual reproduction.[3]

Human use

Historically, Hypnum mosses were used to stuff bedding because they were falsely believed to have sleep-inducing properties.[2][3]

Hypnum curvifolium, commonly known as "sheet moss", is used by some florists.[6]

Species

The number of species in the genus is unresolved. Depending on the source, the number of species ranges from around 50 to 220,[3][5] or (according to GBIF) up to 773.[7]

Some of the species in the genus are:

  • Hypnum acanthoneuron Schwägr.[1]
  • Hypnum acanthophyllum Mont.[1]
  • Hypnum circinale Hook.[8]
  • Hypnum crispifolium Hook.[8]
  • Hypnum cupressiforme Hedw.[8]
  • Hypnum curvifolium Hedw.[9]
  • Hypnum involuta (Hedw.) P.Beauv.[10]

Former species
  • H. leptothallum (Müll.Hal.) Paris,[10] now a synonym of Eurohypnum leptothallum Ando, 1966[11]

References
  1. "Hypnum Hedw". www.gbif.org. Retrieved 22 February 2021.
  2. "carpet moss | Description & Facts | Britannica". www.britannica.com. Retrieved 2022-05-01.
  3. "Hypnum in Flora of North America @ efloras.org". www.efloras.org. Retrieved 2022-05-01.
  4. "Hypnum moss (Hypnum cuppressiforme) – life4oakforests.eu". Retrieved 2022-05-01.
  5. Allaby, Michael (2013-04-18), "Hypnum", A Dictionary of Plant Sciences, Oxford University Press, doi:10.1093/acref/9780199600571.001.0001/acref-9780199600571-e-3413, ISBN 978-0-19-960057-1, retrieved 2022-04-07
  6. "sheet moss | Description & Facts | Britannica". www.britannica.com. Retrieved 2022-05-01.
  7. "Hypnum Hedw". www.gbif.org. Retrieved 15 September 2022.
  8. "Hypnum Hedw". www.gbif.org. Retrieved 2022-04-07.
  9. "Hypnum Hedw". www.gbif.org. Retrieved 2022-05-01.
  10. Cao, Wei; Xiong, Yuanxin; Zhao, Degang; Tan, Hongying; Qu, Jiaojiao (January 2020). "Bryophytes and the symbiotic microorganisms, the pioneers of vegetation restoration in karst rocky desertification areas in southwestern China". Appl Microbiol Biotechnol. 104 (2): 873–891. doi:10.1007/s00253-019-10235-0.
  11. "Hypnum leptothallum (Müll.Hal.) Paris". www.gbif.org. Retrieved 15 September 2022.
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