1. Department of Systematic Botany, Evolutionary Biology Centre, Uppsala University Norbyvägen 18D, SE-752 36 Uppsala, Sweden
2. Department of Palaeobotany, Swedish Museum of Natural History P.O. Box 50007, SE-104 05 Stockholm, Sweden
3. The Bergius Foundation at the Royal Swedish Academy of Sciences P.O. Box 50017, SE-104 05 Stockholm, Sweden; E-mail: birgitta.bremer@bergianska.se