Scanning electron microscopy revealed abundant stomates in the epidermis of the appendix tissue of voodoo lily (Sauromatum guttatum Schott). The stomates were closed before and after the day of flowering climacteric (D-day), but were fully open at the time of peak metabolic activity. The rate of metabolic heat production, as determined by microcalorimetry, was completely dependent on oxygen availability. The highest heat rates were obtained from D-Day appendix tissue in 100% oxygen, the smallest bits of tissue having the highest rates (9100 mu W mg(-1) dry wt.). Metabolic rates were lower for larger pieces of tissue or for tissue in air or nitrogen compared with oxygen. Even a thin film of water on the tissue surface reduced the respiratory rate. Metabolism of the D-day appendix had a Q(10) of 2.5.