1. Department of Botany, Natural History Museum, Cromwell Road, London SW7 5BD, UK
2. Department of Biology, 257 South 1400 East, University of Utah, Salt Lake City, UT 84112, USA
3. Herbarium, The New York Botanical Garden, Bronx River Parkway at Fordham Road, Bronx, NY 10458, USA
4. USDA, Agricultural Research Service, Department of Horticulture, University of Wisconsin, 1575 Linden Drive, Madison, WI 53706-1590, USA