After his work on the Neotropical species of Caesalpinia (Lewis, 1994; PhD thesis) Lewis was able to recognise broad morphological groups within Caesalpinia s.l. He carried out a preliminary cladistic analysis to show the evolutionary relationships within this complex group (Lewis & Schrire, 1995). The group revised in this excellent book is one of the clades in this analysis and comprises the sections Poincianella and Erythrostemon of Caesalpinia s.l. The revision is not only based on herbarium study, but also on extensive field work in Mexico, Central America, Cuba, and Brazil. Living material of 33 taxa was studied, offering many new characters. The book contains an extensive taxonomic history of the genus showing the difficulties of previous workers with genus delimitation. For the Poineianella-Erythrostemon ‘group’ the nomenclatural confusion is cleared up, but for the other species confusion will persist until they have all been studied across their full geographical ranges. In addition to the complex relations in the genus itself, part of the nomenclatural problems are caused by additional names introduced by regional Flora writers for species with a wide geographical range. Furthermore, there is a morphological section with emphasis on the group in this revision but with links to the variation in Caesalpinia s.l. Shorter sections on seed chemistry, insects, pollen, chromosomes, and biogeography are given at the end of the general part. The largest part of the book consists of the systematic section with the revision of the Poineianella-Erythrostemon ‘group’, a key to the species within the group, and a key to the groups within Caesalpinia s.l. and the related genus Hoffmannseggia in the Neotropics.