We are examining seasonal changes in the extent of embolism in the xylem of Smilax rotundifolia in order to ascertain its strategy for coping with freeze-thaw cavitation. This species is deciduous but perennial and has large vessels (about 150 microns). Though it is possible that S. rotundifolia somehow avoids embolism entirely through the seasonal cycle, this seems highly unlikely because the creation of air bubbles is an inevitable consequence of freezing of water in equilibrium with the atmosphere and no mechanism for preventing freezing of xylem sap has ever been described. Given the repeated freeze-thaw cycles that occur in fall and winter in New England, it seems likely that gas bubbles will ultimately exclude most or all of the xylem over the course of the winter. Therefore, it seems the plant must have some way of expelling gas from the xylem during the spring in order to support transpiration by the new year's growth. This might occur by the well-documented mechanism of root pressure, as occurs in grape, or by some other mechanism, probably involving a more local generation of xylem pressure.