Exine Structure in the ‘Cotuleae’ (Anthemideae, Asteraceae)

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Abstract
Pollen of representatives of all genera previously assigned to the ‘Cotuleae’, as well as Minuria from the Astereae, is described from studies under light microscopy and scanning and transmission electron microscopy. Cotula s. str., Leptinella, Nananthea and Soliva are characterized by exines with anthemoid structure; this supports the conclusion that these are natural members of the tribe Anthemideae. The affinities of the non-anthemoid genera are discussed in the light of data on exine structure. Abrotanella, Ischnea and Centipeda have senecioid exines, while Ceratogyne, Dimorphocoma, Elachanthus, Isoetopsis, Minuria and Plagiocheilus have helianthoid exines. Marked differences are shown between the exines of Abroianella and Ischnea which do not support the existence of a very close affinity between them. Evidence is provided to support the link between Isoetopsis and Elachanthus that has been proposed on the basis of cypsela characters.