Two new South American species of Struthanthus (Loranthaceae) posing a challenge to circumscription of neotropical genera

Two new, closely related species of Struthanth us (Loranthaceae) are described, S. meridionalis from southern Bolivia and S. prancei from northern Brazil, each showing significant deviations from the generic norm in their inflorescence morphology. In both cases, a very high proportion of inflorescences bear bracteolate and/or ebracteolate monads as lateral units rather than the triads which characterize the rest of the genus. The place of inflorescence morphology in the development of generic concepts in small-flowered neotropical Loranthaceae is briefly reviewed, leaving the two new species in Struthanthus for the time being. (C) 2003 The Linnean Society of London.