Study of the angiosperm pollen and leaf record contained in the sediments of the Potomac Group has elucidated the history of early angiosperm diversification. Although records of angiosperm pollen now extend back to the Barremian in a number of areas (see reviews by Doyle, 1977 and 1978), the Potomac sequence is significant because it provides the longest and most complete sample of data on early angiosperm evolution in a context where the pollen and megafloral records can be examined together with the sedimentology. This has provided an unparalleled opportunity for the development of insights into the ecological and adaptive aspects of the initial radiation of the flowering plants.