Thirtythree species are recognized for Syngonium in this first published revision since that of Engler and Krause in 1920. Syngonium (now including Porphyrospatha) is the only member of the tribe Syngonieae (Araceae). The genus includes 4 newly described sections, sect. Oblongatum Croat, sect. Cordatum Croat, sect. Pinnatilobum Croat, and sect. Syngonium Croat, defined by leaf morphology, namely by blades basically oblong, cordate, pinnately lobed, and pedately lobed, respectively.
Eleven new species are described: S. chocoanum (Colombia: Choco), S. dodsonianum (Ecuador: Los Rios), S. foreroanum (Colombia: Choco), S. gentryanum (Peru: Hudnuco), S. glaucopetiolatum (Costa Rica, Panama), S. harlingianum (Ecuador: Pastaza), S. laterinervium (SW Costa Rica, NW Panama), S. llanoense (Panama), S. sparreorum (Ecuador: Cotopaxi), S. steyermarkii (Guatemala and SE Mexico), S. triphyllum (Honduras to Panama).

The genus Syngonium, interpreted here to include the genus Porphyrospatha, is one of two genera of Araceae (the other being Monstera) with a center of diversity in Central America. The following revision of Syngonium includes 33 species of which 11 species are described as new to science. Three species are transferred to Syngonium from other genera, namely Philodendron (2 spp.) and Porphyrospatha (1 sp.).

Although the genus needs more field work, especially in South America, the present revision is the culmination of field work conducted in Central America and northern South America over the past decade.

1 P. A. Schulze Curator of Botany, Missouri Botanical Garden, Post Office Box 299, St. Louis, Missouri 63166.
2 This study was sponsored in part by NSF Grant DEB77-14414AOI. ANN. MISSOURI BOT. GARD. 68: 565-651. 1981.