1. Committee on Evolutionary Biology, University of Chicago, Chicago, Illinois 60637, Department of Botany, the Field Museum, Chicago, Illinois 60605, and Natural Science Department, State College of Florida, Bradenton, Florida 34207
2. Department of Botany, the Field Museum, Chicago, Illinois 60605, and Department of Biology, Indiana University Northwest, Gary, Indiana 46408
3. Department of Biology, University of Hawaii, Hilo, Hawaii 96720
4. Department of Botany, the Field Museum, Chicago, Illinois 60605, and Chicago Botanic Garden, Glencoe, Illinois 60022