LITTLE ICE-AGE TEMPERATURE ESTIMATED BY GROWTH AND FLOWERING DIFFERENCES BETWEEN SUBFOSSIL AND EXTANT SHOOTS OF CASSIOPE TETRAGONA, AN ARCTIC HEATHER

1. A unique opportunity to study conditions for plant growth at the on set of glaciation was offered as a retreating glacier at Ellesmere Isl and, Canada, revealed well-preserved, subfossil plants (411+/-70 radio -carbon years old) of Cassiope tetragona, an arctic dwarf-shrub previo usly used to study climate-related growth of modern plants. 2. Growth and flowering of the ancient and modern shoots of C. tetragona from th e same locality were examined retrospectively. The ancient shoots prod uced leaves in each, and flowers in each except one, of the last 26 ye ars before they died, although this production was significantly lower and less variable among years than in the modern shoots. 3. Predictio ns based on regression between modern plant performance and climatic d ata from the study site imply that the mean July temperature of the pe riod immediately preceding the glaciation of the area was about 0.7 de grees C lower than today, This estimate is independently supported by the correlation between growth and mean July temperature seen today am ong different sites. 4. The results support the idea that the pre-litt le Ice Age plants were killed suddenly by permanent snow embedment and not by glacial movements or temperature limitations as such.