Genus of flowering plants in the sunflower family
Cotula is a genus of flowering plant in the sunflower family. 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 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 : 
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").
Uses.
"Cotula" is used in New Zealand as ground cover for bowling greens, playing fields on which the ball-game of bowls is played.
Footnotes.
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