A contribution to the leaf anatomy and taxomony of Apocynaceae in Africa

This publication comprises two main parts. Part one (Chapter I) deals with the leaf anatomy of Apocynaceae in East Africa, where this family is represented by 77 species in 30 genera.

Out of these, 37 species in 26 genera are examined and these exhibit a wide range of anatomical variations.

Many species can be separated on the basis of their leaf anatomy and many genera are confirmed to be closely related.

The most outstanding anatomical characters include the dorsiventral leaves, presence of laticifers, and bicollateral vascular bundles with intraxylary phloem. Part two (Chapter 2) is a monograph of the apocynaceous subtribe Pleiocarpinae- Plumeriodeae-Carisseae, which comprises of three genera, Hunteria (12 spp.); Pleiocarpa (5 spp.) and Picralima (1 sp.).

The subtribe Pleiocarpinae is restricted to Africa, although one species, Hunteria zeylanica, extends to Asia.

It is easily distinguished from the other members of the tribe Carisseae by the presence of completely apocarpous ovaries, with 2-5 carpels, which are a great exception in the family Apocynaceae. The genus Picralima was first described by Pierre in 1896 and has since remained monotypic.

Its only species, Picralima nitida, is not only exploited for its wood, but also used medicinally in its present distribution area and employed as well as an arrow and a fish poison. In this publication, three new species are described in the genus Hunteria (Roxburgh, 1814, 1824) and one new combination is made. The genus Pleiocarpa (Bentham, 1876) has proved to be a very difficult subject due to insufficient collections and lack of sufficient information from the field.

At present it has 5 species and one doubtful species of which the collections are all either sterile or only bearing fruits.

One new species is described. Parallel to the investigations reported here a taxonomic treatment was prepared for the Flora of Tropical East Africa.

This contribution, covering all the mentioned 30 genera and 77 species, will be submitted to the editors in Kew shortly.