Cytopalynological Study of African Hedyotideae (Rubiaceae)

In the Americas only five or six genera are known in the rubiaceous tribe Hedyotideae (Lewis 1962a(Lewis , 1965)), but in Africa, south of the Sahara and in adjacent islands, at least thirty are found.A cytopalynological study of these genera was undertaken in an attempt to describe their chromosomal complements and pollen forms in the tribe's center of diversity and to compare them with those from the Americas.Such a study should better characterize the tribe in these continents and should develop an understanding of major phylogentic trends in the whole tribe Hedyotideae.Evidence from these disciplines might also improve present classifications by confirming or rejecting certain intergeneric realignments which in the past have been proposed for African members of the tribe.The genera are discussed under four groupings, three with known chromosome numbers, and the fourth unknown.Procedures, materials and results of the chromosomal study are summarized in Appendix 1. Species studied palynologically, together with the techniques involved, are given in Appendix 2. Author citations for species and lower taxa are given in the appendices when these have been studied cytopalynologically. I. BASIC CHROMOSOME NUMBER X = 9.Agathisanthemum Klotzsch An African genus consisting of six species of which three are restricted in distribution, Agathisanthemum is said by Bremekamp (1952) to show a close relationship with the Asian section Diplophragma W. & A. of Hedyotis L., particularly in its form of capsular dehiscence.Among the African members of the Hedyotideae he suggested a close affinity with Dikrachionostylus.The chromosomes of A. hojeri and A. globosum are small and based on x = 9 and resemble those of Oldenlandia and a number of allied genera. 2 Both subspecies 3 of A. hojeri are diploid (n = 9) and A. glohosum is tetraploid (n = 18).1 A portion of this study was completed at the Royal Botanic Gardens, Kew, during the tenure of a John S. Guggenheim Memorial Foundation Fellowship (1963-64).To the director of the