1. Department of Biological Sciences; University of Alberta; Edmonton AB T6G 2E9 Canada
2. Department of Forestry and Horticulture; The Connecticut Agricultural Experiment Station; New Haven CT 06504-1106 USA
3. Department of Plant Agriculture; University of Guelph; 4890 Victoria Av. N., PO Box 7000 Vineland Station ON L0R 2E0 Canada
4. Department of Botany; University of British Columbia; Vancouver BC V6T 1Z4 Canada
5. National Research Council of Canada; Saskatoon SK S7N 0W9 Canada
6. Department of Renewable Resources; University of Alberta; Edmonton AB T6E 2E3 Canada