In botany, a perigynium (plural: perigynia), also referred to as a utricle, typically refers to a sac that surrounds the

achene An achene (; ), also sometimes called akene and occasionally achenium or achenocarp, is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate (formed from one carpel) and indehiscent (they do not ope ...

of plants in the genus ''

Carex ''Carex'' is a vast genus of more than 2,000 species of grass-like plants in the family Cyperaceae, commonly known as sedges (or seg, in older books). Other members of the family Cyperaceae are also called sedges, however those of genus ''Carex'' ...

'' (

Cyperaceae 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'' w ...

). The perigynium is a modified

prophyll In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis or cone scale. Bracts are usually different from foliage leaves. They may be smaller, larger, or o ...

, tissue of leaf origin, that encloses the dry, one-seeded achene. In

liverwort The Marchantiophyta () are a division of non-vascular land plants commonly referred to as hepatics or liverworts. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in which cells of the plant carry only a single set of g ...

s, "perigynium" refers to a tube-shaped structure which encases the

archegonium 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 ...

and the developing

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 ...

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

Dispersal

Features of the perigynium may aid in seed dispersal, such as a surface that clings to fur or skin or a shape that enables dispersion via wind or water. Seed dispersal by animals such as ants (

myrmechory Myrmecochory ( (sometimes myrmechory); from grc, μύρμηξ, mýrmēks ("ant") and ''khoreíā'' ("circular dance") is seed dispersal by ants, an ecologically significant ant–plant interaction with worldwide distribution. Most myrmeco ...

) has been recorded, as some species of sedges have developed

elaiosome Elaiosomes ( grc, ἔλαιον ''élaion'' "oil" + ''sóma'' "body") are fleshy structures that are attached to the seeds of many plant species. The elaiosome is rich in lipids and proteins, and may be variously shaped. Many plants have elaio ...

s 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.

Perigynium vs. utricule

The terms perigynium and utricle have been widely used interchangeably. In North America, the term perigynia is preferred, while utricle is more commonly used in Europe. After the merging of ''

Kobresia ''Kobresia'' is a genus of plants in the sedge family. They are sometimes called bog sedges. These perennial sedges are quite similar to ''Carex'' species in appearance. The genus is widespread across much of Europe, Asia and North America, with ...

'' under ''

'', a terminological clarification was desired, as the open prophyll of ''

'' 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 ''

'' ''sensu lato'' (including former ''

''), but calling it utricle when it has its margins fused so it is entirely closed (as in the vast majority of ''

'' species).

References

{{Reflist, refs= {{cite journal , last1=ABUDUREHEMAN , first1=B. , last2=CHEN , first2=Y. , last3=LI , first3=X. , last4=ZHANG , first4=L. , last5=LIU , first5=H. , last6=ZHANG , first6=D. , last7=GUAN , first7=K. , title=Patterns of Reproductive and Seed Dispersal and Ecological Significance of the Clonal Spring Ephemeroid Plant Carex physodes in the Gurbantuggut Desert , journal=Planta Daninha , date=29 March 2018 , volume=36 , doi=10.1590/s0100-83582018360100007, doi-access=free Carter, R. 1993. Animal Dispersal of the North American Sedge, ''Cyperus plukenetii'' (Cyperaceae). American Midland Naturalist, Vol. 129, No. 2. pp. 352-356. {{cite book , last1=Wilhelm , first1=Gerould , last2=Rericha , first2=Laura , date=2017 , title=Flora of the Chicago Region: A Floristic and Ecological Synthesis , publisher=Indiana Academy of Sciences Handel, S.N. 1976. Dispersal ecology of ''Carex pedunculata'' (Cyperaceae), a new North American myrmechore. Amer. J. Bot. 63 (8): 1071-1079. {{cite book , last1=Harris, first1=James G., date=2001 , title=Plant Identification Terminology: An Illustrated Glossary, edition=2nd, location=Payson, Utah, publisher=Spring Lake Publishing, page=131 , isbn=0-9640221-6-8 {{cite journal , last1=Jiménez-Mejías , first1=Pedro , last2=Luceño , first2=Modesto , last3=Wilson , first3=Karen L. , last4=Waterway , first4=Marcia J. , last5=Roalson , first5=Eric H. , title=Clarification of the Use of the Terms Perigynium and Utricle in ''Carex'' L. (Cyperaceae) , journal=Systematic Botany , date=1 September 2016 , volume=41 , issue=3 , pages=519–528 , doi=10.1600/036364416X692488, s2cid=89281001 {{cite web , title=''Carex'' , url=https://michiganflora.net/genus.aspx?id=Carex , website=Michigan Flora Online , access-date=6 July 2019 {{cite web , title=A Grammatical Dictionary of Botanical Latin , url=http://www.mobot.org/mobot/latindict/keyDetail.aspx?keyWord=perigynium , website=www.mobot.org , access-date=6 July 2019 {{cite book , author1=Robert H. Mohlenbrock , author2=Paul Wayne Nelson , year=1999 , title=Sedges: ''Carex'' , series=Volume 14 of The Illustrated flora of Illinois , publisher=

Southern Illinois University Press Southern Illinois University Press or SIU Press, founded in 1956, is a university press located in Carbondale, Illinois, owned and operated by Southern Illinois University. The press publishes approximately 50 titles annually, among its more tha ...

, isbn=978-0-8093-2074-5 , chapter=Introduction , pages=3–7 , chapter-url=https://books.google.com/books?id=1ZGekaNQ4YAC&pg=PA3 Fruit morphology Carex