| Juncus | |
|---|---|
 | |
| Habit ofJ. conglomeratus | |
 | |
| Flower ofJ. squarrosus showing: 6 spreading tepals, anthers (upright yellow, held on white filaments), ovary (green) with stigma (pinkish tip column) and styles (white) | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Monocots |
| Clade: | Commelinids |
| Order: | Poales |
| Family: | Juncaceae |
| Genus: | Juncus L. |
| Type species | |
| Juncus acutus | |
| Synonyms[1] | |
| |
Juncus is agenus ofmonocotyledonousflowering plants, commonly known asrushes. It is the largest genus in the familyJuncaceae, containing around 300 species.[2]
Rushes of the genusJuncus areherbaceous plants that superficially resemblegrasses orsedges.[3] They have historically received little attention from botanists; in his 1819monograph,James Ebenezer Bicheno described the genus as "obscure and uninviting".[4]
The form of the flower differentiates rushes from grasses or sedges. The flowers ofJuncus comprise fivewhorls of floral parts: three sepals, three petals (or, taken together, six tepals), two to sixstamens (in two whorls) and astigma with three lobes.[3] The stems are round in cross-section, unlike those ofsedges,[3] which are typically somewhat triangular in cross-section.[5]
InJuncus sectionJuncotypus (formerly calledJuncus subg.Genuini),[6] which contains some of the most widespread and familiar species, the leaves are reduced to sheaths around the base of the stem and thebract subtending the inflorescence closely resembles a continuation of the stem, giving the appearance that the inflorescence is lateral.[7]
Juncus has acosmopolitan distribution, with species found throughout the world, with the exception ofAntarctica.[2] They typically grow in cold or wet habitats, and in the tropics, are most common inmontane environments.[3]
Severalfossil fruits of aJuncus species have been described frommiddle Miocenestrata of the Fasterholt area nearSilkeborg in CentralJutland,Denmark.[8]
The genusJuncus was first named byCarl Linnaeus in his 1753Species Plantarum. Thetype species of the genus was designated byFrederick Vernon Coville, who in 1913 chose the first species in Linnaeus' account,Juncus acutus.[6]Juncus can be divided into two major groups, one group withcymoseinflorescences that includebracteoles, and one withracemose inflorescences with no bracteoles.[6]
The genus is divided into the followingsubgenera andsections:[6]
Plants of the World Online accepts the following species in the genusJuncus:[9]
