Juncus

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Juncus
Juncus.conglomeratus.2.jpg
Habitus of J. conglomeratus
Juncus.squarrosus3.-.lindsey.jpg
Flower of J. squarrosus
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Monocots
(unranked): Commelinids
Order: Poales
Family: Juncaceae
Genus: Juncus
L.
Type species
Juncus acutus
L.

Juncus is a genus of monocotyledonous flowering plants, commonly known as rushes. It is the largest genus in the family Juncaceae, containing around 300 species.[1]

Description[edit]

Rushes of the genus Juncus are herbaceous plants that superficially resemble grasses or sedges.[2] They have historically received little attention from botanists; in his 1819 monograph, James Ebenezer Bicheno described the genus as "obscure and uninviting".[3]

The form of the flower differentiates rushes from grasses or sedges. The flowers of Juncus comprise five whorls of floral parts: 3 sepals, 3 petals (or, taken together, 6 tepals), 2–6 stamens (in two whorls) and a stigma with three lobes.[2] The stems are round in cross-section, unlike those of sedges,[2] which are typically somewhat triangular in cross-section.[4]

In Juncus section Juncotypus (formerly called Juncus subg. Genuini),[5] which contains some of the most widespread and familiar species, the leaves are reduced to sheaths around the base of the stem and the bract subtending the inflorescence closely resembles a continuation of the stem, giving the appearance that the inflorescence is lateral.[6]

Distribution and ecology[edit]

Juncus has a cosmopolitan distribution, with species found throughout the world, with the exception of Antarctica.[1] They typically grow in cold or wet habitats, and in the tropics, are most common in montane environments.[2]

Classification[edit]

In Juncus effusus (and other species in J. sect. Juncotypus), the bract appears as a continuation of the stem, and the inflorescence appears lateral.

The genus Juncus was first named under the rules of the International Code of Nomenclature for algae, fungi, and plants by Carl Linnaeus in his 1753 Species Plantarum. The type species of the genus was designated by Frederick Vernon Coville in 1913; he chose the first species in Linnaeus' account, which was Juncus acutus.[5] Juncus can be divided into two major groups, one group with cymose inflorescences that include bracteoles, and one with racemose inflorescences with no bracteoles.[5]

The genus is divided into the following subgenera and sections:[5]

  • Juncus subg. Juncus
  1. sect. Juncus
  2. sect. Graminei (Engelm.) Engelm.
  3. sect. Caespitosi Cout.
  4. sect. Stygiopsis Kuntze
  5. sect. Ozophyllum Dumort.
  6. sect. Iridifolii Snogerup & Kirschner
  • Juncus subg. Poiophylli Buchenau
  1. sect. Tenageia Dumort.
  2. sect. Steirochloa Griseb.
  3. sect. Juncotypus Dumort.
  4. sect. Forskalina Kuntze

Species[edit]

The Plant List accepts the following species in the genus Juncus:[7]

References[edit]

  1. ^ a b Ralph E. Brooks & Steven E. Clemants (2000). "Juncus". Magnoliophyta: Alismatidae, Arecidae, Commelinidae (in part), and Zingiberidae. Flora of North America 22. Oxford University Press. ISBN 0-19-513729-9. 
  2. ^ a b c d D. M. D. Yakandawala, U. M. Sirisena & M. D. Dassanayake (2005). "Two new records of Juncus species (rush family – Juncaceae) in Sri Lanka" (PDF). Ceylon Journal of Science 33: 67–76. 
  3. ^ James Ebenezer Bicheno (1819). "XVII. Observations on the Linnean genus Juncus, with the characters of those species, which have been found growing wild in Great Britain". Transactions of the Linnean Society of London 12 (2): 291–337. doi:10.1111/j.1095-8339.1817.tb00229.x. 
  4. ^ Peter W. Ball, A. A. Reznicek & David F. Murray. "210. Cyperaceae Jussieu". In Flora of North America Editorial Committee. Magnoliophyta: Commelinidae (in part): Cyperaceae. Flora of North America 23. Oxford University Press. ISBN 978-0-19-515207-4. 
  5. ^ a b c d Jan Kirschner, Lázaro J. Novara , Vladimir S. Novikov, Sven Snogerup & Zdeněk Kaplan (1999). "Supraspecific division of the genus Juncus (Juncaceae)". Folia Geobotanica 34 (3): 377–390. doi:10.1007/BF02912822. JSTOR 4201385. 
  6. ^ K. L. Wilson & L. A. S. Johnson (2001). "The genus Juncus (Juncaceae) in Malesia and allied septate-leaved species in adjoining regions" (PDF). Telopea 9 (2): 357–397. 
  7. ^ "Juncus". The Plant List. Retrieved October 23, 2013. 

External links[edit]

  • Media related to Juncus at Wikimedia Commons
  • Data related to Juncus at Wikispecies