History and Infrageneric Nomenclature of Philodendron (Araceae)

Abstract

Summary. An historical review of the systematics of Philodendron Schott is presented, from the earliest known records to modern studies; the classifications of Schott and Engler are discussed in detail. A nomenclatural revision of infrageneric taxon names is given, with synonymy and lectotypification. horticulture. For taxonomist and horticulturist alike, the circumscription and identifica- tion of the species remain the most pressing problems in the absence of any general revision more recent than Krause's treatment for 'Das Pflanzenreich' (Krause 1913). Being primarily a rainforest group, Philodendron has its richest diversity in some of the botanically poorest-known regions of tropical America such as the Choc6 of Colombia, subandean Peru and Ecuador and the western part of lowland Amazonia. As a consequence, many new taxa certainly await discovery or formal recognition and at present it is impossible to ascertain accurately the true size of the genus. The infrageneric taxonomy is also in need of revision. In a recent study based primarily on inflorescence characters, I proposed three subgenera rather than the two recognized by previous authors and suggested that sever- al of the sections were probably not natural (Mayo 1986b). Much further investigation is required of the largest subgenus, subgen. Philodendron, but it seems likely that inflorescence and floral morphology and anatomy are suf- ficiently variable to provide a useful basis for extending and improving the infrageneric classification. Studies of other characters would also be highly desirable. Recently, botanists have begun to pay more attention to the genus (see below), and it is very probable that the next decade will see new proposals for the infrageneric classification. The present paper is therefore offered as an aid to future revisionary studies of the genus. The history of the genus Philodendron began with a very short description by Schott (1829). His laconic article was concerned with separating two new genera of Araceae, Philodendron and Syngonium, from the hitherto heter- ogeneous Caladium. The article was one of a series by Schott which listed new garden plants and, almost as an aside, dealt with generic limits in Araceae. Though seemingly trivial at first glance, Schott's new generic concepts marked perhaps the most important historical advance in the systematics of