Hardy plants of both cabbage and Saxifraga cordifolia showed definite increases in frost hardiness (2 - 6[degree]C) as a result of infiltration with molar glycerine solutions, followed by evaporation of the water so absorbed. In the case of cabbage, the increases in hardiness agreed very well with the calculated increases on the basis of a purely osmotic effect. In the case of Saxifraga, the increases were somewhat less than expected. It is suggested that the results with Saxifraga are related to the lower temperatures that this plant can survive. The increased stiffening of the protoplasm with the drop in temperature may partly counteract the osmotic protection by slightly reducing the tolerance of dehydration.