P. sect. Polytomium (Schott) Engl.,
Martius, Fl. Bras.
TYPE: P. radiatum Schott (designated by Mayo, 1990).
The section is a small group of 7-8 species with pinnately or bipinnately lobed leaves from the West Indies, Central America and northern South America. Plants are vines or appressed climbers with more or less terete petioles, generally deeply lobed, large, moderately coriaceous blades and flowers with several axillary or sub-basal ovules per locule. Only one species, P. distantilobum K. Krause was reported for the Amazon basin, but another species, P. pinnatifidum, placed erroneously I believe, in P. sect. Macrogynium, really belongs here as well. It is also a species occurring in the upper Amazon basin. Two additional species, P. angustisectum and P. elegans K. Krause occur in northwestern South America in Colombia. Philodendron fendleri occurs in Trinidad and northern Venezuela and P. lacerum (Jacq.) Schott occurs in the Greater Antilles (Cuba, Jamaica and Hispaniola). One poorly known species, P. houlettianum Engl. is reported from French Guiana but no material exists to confirm what it is. The most widespread species in the section P. radiatum, occurs in Central America, ranging from Mexico (San Luis Potosí) to Colombia (Antioquia). Philodendorn radiatum var. pseudoradiatum is endemic to Chiapas State of Mexico. Central American species in P. sect. Polytomium are P. warszewiczii ranging from Mexico to Nicaragua and P. dressleri which is endemic to Mexico.
Mayo (1986), following a cladistic survey of inflorescence types, concluded that P. fendleri, belonged in a group with P. melinonii and P. pedatum. Based on overall morphology I would conclude that the three species are not closely related. The latter is, in my opinion, a member of a very distinctive section, P. sect. Schizophyllum. Philodendron melinonii Brongn. ex Regel, a distinctive species with cordate blades and placed by Krause in P. sect. Macrolonchium, is in my opinion, not related to either of the sections with lobed leaves.