THE STRUCTURE AND FUNCTION OF THE PRIMITIVE ANGIOSPERM FLOWER - A DISCUSSION*

Abstract

Morphological and functional features of primitive entomophilous Angiosperm flowers are discussed and confronted with modem conceptions on early Angiosperm differentiation. Evidence is put forward to show that large, solitary and terminally-borne flowers are not most primitive in the Angiosperms, but rather middle-sized ones, grouped into lateral flower aggregates or inflorescences. It is believed that most primitive, still unspecialized Angiosperm flowers were pollinated casually by beetles. Only in a later phase did they gradually become adapted to the more effective but more devastating type of beetle pollination. Together with this specialization, flower enlargment, reduction of inflorescences, numerical increase of stamens and carpels, and their more dense aggregation and flattening might have occurred. In regard to pollination, many primitive Angiosperms have maintained the archaic condition of cantharophily, because beetles are still a dominant insect group, whereas in dispersal they have been largely forced to switch over from the archaic saurochory to the more modern modes of dispersal by birds and mammals, since during the later Mesozoic the dominance of reptiles had come to an end.