POLLEN MORPHOLOGY OF AGAVACEAE AND SOME RELATED GENERA

Pollen grains of 73 species of the genera Agave, Beschorneria, Bravoa, Clistoyucca, Furcreae, Hesperaloe, Hesperocallis, Hesperoyucca, Hosta, Leucocrinum, Manfreda, Polianthes, Prochnyanthes, Pseudobravoa, Samuela and Yucca were examinedby light and scanning electron microscopy. Eight pollen types and four subtypes are recognized based on the presence of tetrads or monads, the number and type of the apertures and the characters of its margins and the exine sculpture. The evolutionary trends of the pollen characters are discussed. Pollen morphology supports the exclusion of Hosta, Hesperocallis and Leucocrinum from the Agavaceae and shows that the phylogenetical relationships between these genera are still obscure. The relationships between the different tribes of Agavaceae and their genera are discussed based on the present results and floral morphology in relation with possible pollination agents.