B.A., Columbia University, 1953.
M.Sc., Cornell University, 1958.
Ph.D., Washington University, 1961.

Chair, Department of Botany, Field Museum of Natural History, 1978-1985.

Flora of Costa Rica/speciation and species richness in Costa Rican flowering plants/early evolution of angiosperms and processes of angiosperm diversification.

The Flora Costaricensis is an encyclopedia-like review of the native and naturalized plants of Costa Rica, with keys, illustrations, descriptions and short discussions. It is published in parts, each covering a single large family or several smaller families. The work attempts to define and characterize the species and facilitate user identification.

The flowering plants of Costa Rica probably number close to 10,000 species, packed into an area about the size of West Virginia. Taxonomic review of many unrelated families has disclosed repeated geographic and altitudinal patterns, while making it clear that closely related species rarely grow in the same habitat. Analysis of these patterns may give us insights into the speciational processes that have helped produce so rich a flora.

The early evolution of angiosperms is poorly understood, while the origin of angiosperms is still as much an "abominable mystery" as when Darwin so described it. Current thinking about early angiosperm evolution continues a tradition of more than fifty years and is virtually unanimous. By exploring radically different scenarios it may be possible to develop new insights into early morphological trends, or at least challenge the confidence of current thinking in the field.