POLLEN PRESENTERS IN THE SOUTH-AFRICAN FLORA

In contrast with the majority of flowering plants, where pollen is rel eased directly from the anthers to travel to the female organ to effec t fertilization, the pollen in certain species belonging to fifteen fa milies worldwide is initially deposited on the female part of the flow er before transport to another flower occurs. The structure on which t he pollen is deposited is (in almost all cases) a modification of the style called the pollen presenter. In South Africa, pollen presenters are ubiquitous in the Asteraceae, Campanulaceae, Lobeliaceae, Goodenia ceae and Proteaceae; they also occur in almost half of the genera in t he Rubiaceae, and in Polygala and some Muraltia (Polygalaceae), in Tur raea, Trichilia and Ekebergia (Meliaceae) and a small proportion of ta xa in the Fabaceae. The modifications of the style take various forms and can be summarized into actively and passively operating types. The active forms act like a piston to push the pollen away from the anthe rs, while the passive forms are static, receiving the pollen from the anthers before the anthers fall away to leave the pollen ready to be r emoved from the presenter by animals or the wind. In the past, pollen presenters have either not been recognized or have been described as s tyles or stigmas. This leads to confusion about processes involved in pollination and wastes useful information which is of value in taxonom ic studies.