# Perigynium

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In botany, a **perigynium** (plural: **perigynia**), also referred to as a **utricle**, typically refers to a sac that surrounds the [achene](/source/Achene) of plants in the genus *[Carex](/source/Carex)* ([Cyperaceae](/source/Cyperaceae)).[1][2] The perigynium is a modified [prophyll](/source/Prophyll), also known as a [glume](/source/Glume), which is tissue of leaf origin that encloses the dry, one-seeded achene.[3]

In [liverworts](/source/Liverwort), "perigynium" refers to a tube-shaped structure that encases the [archegonium](/source/Archegonium) and the developing [sporophyte](/source/Sporophyte).[4]

The location, size, shape, hairiness, color, and other aspects of the perigynium are important structures for distinguishing *Carex* species.[5] They are often subtended by a scale, which may also aid in identification.[5]

## Dispersal

Features of the perigynium may aid in seed dispersal, such as a surface that clings to fur or skin[6] or a shape that enables dispersion via wind or water.[7] Seed dispersal by animals such as ants ([myrmechory](/source/Myrmechory)) has been recorded, as some species of sedges have developed [elaiosomes](/source/Elaiosome) at the base of the perigynia. Ants carry the perigynium back to the nest, use the elaiosome for food, and the seed germinates away from the parent plant.[8]

## Perigynium vs. utricule

The terms perigynium and utricle have been widely used interchangeably.[9] In North America, the term perigynium is preferred, while utricle is more commonly used in Europe.[9] After the merging of *[Kobresia](/source/Kobresia)* under *[Carex](/source/Carex)*, a terminological clarification was desired, as the open prophyll of *Kobresia* could not be assimilated to the concept of utricle, which etymologically implies closure. The authors of a 2016 paper recommended using perigynium to refer generically to the flower prophyll of *Carex* *sensu lato* (including former *Kobresia*), but calling it utricle when it has its margins fused so it is entirely closed (as in the vast majority of *Carex* species).[9]

## References

1. Harris, James G. (2001). *Plant Identification Terminology: An Illustrated Glossary*. 2nd ed. Payson, Utah: Spring Lake Publishing. p. 131. ISBN 0-9640221-6-8.

1. Wilhelm, Gerould & Rericha, Laura (2017). *Flora of the Chicago Region: A Floristic and Ecological Synthesis*. Indiana Academy of Sciences.

1. Robert H. Mohlenbrock & Paul Wayne Nelson (1999). ["Introduction"](https://books.google.com/books?id=1ZGekaNQ4YAC&pg=PA3). *Sedges:*Carex'**. Volume 14 of The Illustrated flora of Illinois. [Southern Illinois University Press](/source/Southern_Illinois_University_Press). pp. 3–7. ISBN 978-0-8093-2074-5.**

1. ["A Grammatical Dictionary of Botanical Latin"](http://www.mobot.org/mobot/latindict/keyDetail.aspx?keyWord=perigynium). *www.mobot.org*. Retrieved 6 July 2019.

1. ["*Carex*"](https://michiganflora.net/genus.aspx?id=Carex). *Michigan Flora Online*. Retrieved 6 July 2019.

1. Carter, R. 1993. Animal Dispersal of the North American Sedge, *Cyperus plukenetii* (Cyperaceae). American Midland Naturalist, Vol. 129, No. 2. pp. 352-356.

1. ABUDUREHEMAN, B.; CHEN, Y.; LI, X.; ZHANG, L.; LIU, H.; ZHANG, D.; GUAN, K. (29 March 2018). "Patterns of Reproductive and Seed Dispersal and Ecological Significance of the Clonal Spring Ephemeroid Plant Carex physodes in the Gurbantuggut Desert". *Planta Daninha*. **36**. [doi:10.1590/s0100-83582018360100007](https://doi.org/10.1590/s0100-83582018360100007)

1. Handel, S.N. 1976. Dispersal ecology of *Carex pedunculata* (Cyperaceae), a new North American myrmechore. Amer. J. Bot. 63 (8): 1071-1079.

1. Jiménez-Mejías, Pedro; Luceño, Modesto; Wilson, Karen L.; Waterway, Marcia J.; Roalson, Eric H. (1 September 2016). "Clarification of the Use of the Terms Perigynium and Utricle in *Carex* L. (Cyperaceae)". *Systematic Botany*. **41** (3): 519–528. [Bibcode:2016SysBo..41..519J](https://ui.adsabs.harvard.edu/abs/2016SysBo..41..519J). [doi:10.1600/036364416X692488](https://doi.org/10.1600/036364416X692488). [S2CID 89281001](https://api.semanticscholar.org/CorpusID:89281001)

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