After the family Asteraceae, the family Orchidaceae represents one of the two largest families of flowering plants. Its number of species currently stands at 27,732 divided over 773 genera. Note that five of the thirty largest genera of flowering plants are Orchids, the largest being the genus Bulbophyllum with 1800 species . In tropical Africa there are an estimated 1100 to 1200 species of orchids.
This first volume devoted to orchids gathers 555 species (plus another 13-14 of unconfirmed status). It begins with a bibliography citing recent books and articles, that is to say, published after Enumeration des Plantes d'Afrique Tropicale Volume 3 (1995), and Volume 4 (1997).
As with previous volumes in this series, genera and species are presented alphabetically. For each species of references as well as data concerning illustrations are indicated. The synonymy is vast, completing the one in Enumeration des Plantes d'Afrique Tropicale, Volume 3.
Given the great interest in orchids, morphological descriptions are provided, as well as ecological description, furthermore, a distribution map in tropical Africa is presented.
In the study area, the most speciose genera are Eulophia 117 (5?), Bulbophyllum 87 (+ 1 or 2), Dira 52 (+ 2?), Angraecum 48, Disperis 37 (+2), Aerangis 30, Diaphananthe 26 (+ 3?), Brachycorythis 21, Angraecopsis 19, Ancistrorlynchus 18, and Cynorchis and Cyrtorchis 17 species each.