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Eurotia lanata (Pursh) Moq. [Krascheninnikovia lanata (Pursh) Guldenstaedt.] (winterfat) is a boreal cold-desert subshrub, seldom more than 2 ft tall, that thrives in dry climates at cool temperatures. Diaspore collections from Saskatchewan, Wyoming, Colorado, and New Mexico were cleaned and placed on moistened filter paper in petri dishes. Seeds maintained at 0, 5, 10, 15, and 20degreesC for seven days germinated at all temperatures with no evidence of acclimation. At radicle emergence (ca. 3 mm), seeds were placed in calorimeter ampoules. Heat rate (R-q) was measured at a given temperature, then a vial containing NaOH solution was added to measure the rate of CO2 evolution (R-CO2) for the same tissue at the same temperature. This procedure was repeated for each of the populations at temperatures ranging from 0 to 25degreesC. Metabolic efficiency and predicted specific growth rates were calculated from these measurements. Optimum temperature for germination, metabolism, and early seedling growth ranged from 5 to 25degreesC. Seedlings differed in response to temperature reflecting the climate at the site of origin. Published by Elsevier Science B.V.