| Abstract: |
The pollen morphology of 124 taxa of the tribe Ranunculeae (Ranunculaceae) was investigated by light & scanning electron miscroscopy. Ten pollen types are recognized, mainly based on the types of columellae & aperture & on the nature of the tectum. Nine evolutionary trends, based on pollem morphological characters, are proposed. Tricolpate pollen is common & represents the basic condition. Pericolpate & periporate pollen represent derivative conditions. Periporate pollen is found in groups of closely related species, & this condition has evolved independently several times. Some lowland Ranunculus species of Australia & New Zealand show Antarctic, others Malesian affinities. The alpine New Zealand Ranunculus species have South American affinities. The genus Adonis should be removed from the tribe Ranunculaceae, within which the following genera are accepted: Callianthemum, Hamadryas, Laccopetalum, Myosurus, Paroxygraphis, Ranunculus & Trautvetteria. Pollen morphology supports the subdivision of Adonis into two sections, Consiligo & Adonis. The development of oblate pollen with polar caps in sect. Adonis has probably taken place in response to aridity. The genus Laccopetalum is distinct, but closely related to Ranunculus sect. Trollianthoideae. The annual Eurasiatic species of Ranunculus with sculptured achenes can be referred to two sections, viz. sect. Ranunculus & sect. Echinella.
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