This monograph covers geographically southern Chad, Cameroon, Equatorial Guinea, Sao Tome and Principe, the Central African Republic (CAR), Gabon, the Republic of Congo, the Democratic Republic of Congo (DRC, referred to until recently as Zaire) and northern Angola. Introductory chapters (geography, relief, hydology, climate, history, vegetation, environmental degredation and conservation, history of botanical exploration, materials and methods) followed by systematic part (Natural key to the African subfamilies/ Subfamily Orchidoideae/ Sunfamily Tropidoideae (Pfitzer)/ Subfamily Spiranthoideae (Dressler)/ Subfamily Nettioideae Lindl./ Subfamily Vanilloideae (Lindl.)