THE SYSTEMATIC VALUE OF ENDEXINE ORNAMENTATION IN SOME PSYCHOTRIEAE POLLEN (RUBIACEAE-RUBIOIDEAE)

An examination of the endexine in pollen from 22 species in five gener a (mainly African) of the Psychotrieae allows a preliminary survey of endexine Variation in this large tribe. The endexine surface varies fr om smooth (Chazaliella) to flocky (Chassalia) or granular (Psychotria, Gaertnera and Pagamea). The granulation of the three latter genera is interrupted by endocracks. There are no proper endoapertures, but in Gaertnera and Pagamea, apparent endexine thickenings (''costae'') occu r at the polar ends of the mesoapertures. Therefore, endexine characte rs have systematic importance at the generic level in this tribe. The results also indicate pollen morphological differences between the sub genera Psychotria and Tetramerae of Psychotria.