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''Cotula'' is a genus of flowering plant in the sunflower family.〔(Linnaeus, Carl von. 1753. Species Plantarum 2: 891-892 ) in Latin〕〔(Tropicos, ''Cotula'' L. )〕 It includes plants known generally as water buttons or buttonweeds. The species within this genus can vary extensively in their habit, leaf division, involucre, receptacle and achenes. This makes it difficult to define them by comparing their morphology. The genus can only be defined by looking at the corollas of their flowers. Most are disciform (lacking ray florets). These corollas may be tubular, reduced or even absent. Another characteristic is their solitary heads growing on a peduncle. == Taxonomy == ''Cotula'' is the largest genus found in the Southern Hemisphere of the tribe Anthemideae. This genus was first mentioned by Carl Linnaeus, who described four species in his first edition (1753) of ''Species Plantarum''. In 1867 the genus was subdivided by George Bentham〔Bentham, G., 1867: "Flora Australiensis", Vol. 3. Reeve, London.〕 into three sections. Since his account, only a few changes have been made but the number of species has remained more or less stable. The sections possess different basic chromosome numbers : *section ''Cotula'' : largest section with about 40 species; mostly in South Africa, a few in North Africa and Australia + the cosmopolitan species ''C. coronopifolia'' and the widespread species ''C. turbinata;'' this section also includes the former genera ''Cenia'' and ''Otochlamys''; basic chromosome numbers x = 8 and x = 10. *section ''Strongylosperma'' (Less.) Benth.: a total of eight species, found in warmer parts of Africa and Asia (often lumped as ''C. anthemoides''), Central and South America (''C. mexicana'') and Australia (five species, including ''C. australis''); basic chromosome number : x = 18 *section ''Leptinella'' (Cass.) Hook f. : the remaining thirty species, found in South America and the Falkland Islands (the type species ''C. scariosa''), New Zealand, the Subantarctic Islands (together 24) and five species from Australia and New Zealand.; the species in this section have a distinctive characteristic not found in the other sections : inflated pistillate corollas; basic chromosome number : x = 13. See also ''Leptinella''. David G. Lloyd has proposed that the five species from Australia and New Guinea are distinctive enough from the other species from the section ''Leptinella'' to be brought under a new section with the proposed name ''Oligoleima'' (type species ''C. longipes''). ;Species〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cotula」の詳細全文を読む スポンサード リンク
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