1. Illinois State Museum, Research and Collections Center, 1920 South 10½ Street, Spring-field, IL 62703
2. Department of Plant Biology and Institute for Quaternary Studies, University of Maine, Orono, ME 04469
3. Department of Botany, Trinity College, Dublin 2, Ireland
4. Limnological Research Center, University of Minnesota, Minneapolis, MN 55455
5. Department of Geological Sciences and Institute for Quaternary Studies, University of Maine, Orono, ME 04469