Investigations of Angiosperms From the Middle Eocene of North America: Flowers of the Celtidoideae

Flowers from the Middle Eocene Claiborne Formation of western Tennessee have both floral and palynological features suggestive of affinities with the subfamily Celtidoideae of the Ul‐maceae. Floral size, pollen size, and exine structure suggest that these flowers are intermediate between insect‐pollinated ancestors and the modern wind‐pollinated Celtidoideae. Thus, they represent the first direct fossil evidence supporting the widespread notion that at least some of the Amentiferae have been derived from insect‐pollinated ancestors.