Two new species of Xanthosoma (Araceae) from South America and notes on the tribe Caladieae

Abstract

Two new species of Xanthosoma sect. Acontias, X. mariae and X. latestigmatum, are described and il- lustrated. They have pilose, pedate leaf blades as have in Xanthosoma only X. plowmanii and X. pottii, and their pollen grains are released as monads, unlike in all other Xanthosoma species, which, as far as studied, release the pollen in tetrads. X. mariae is an evergreen plant mainly distinguished by its dark green velvety lustrous leaf blades with numerous leaflets and tuber-like swellings at the junction of petiole and blade; the gynoecium is of the Acontias type and the ovary is pilose in the lower part. X. latestigmatum is seasonally dormant and has medium green leaf blades with numerous leaflets and no tuber-like swellings; the gynoecium is of the Caladium type (with a very broad stigma) and completely glabrous. The relationship of the genera Caladium and Xanthosoma is discussed, C. paradoxum is transferred to Xanthosoma and the new combination X. paradoxum validated, and a key to the genera of the tribe Caladieae given.