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The present controversial status of the problem of transport rate as related to temperature is briefly summarized in a recent paper by WENT and HULL (8). As pointed out by these authors, the reported Qlo values for translocation range from less than 1 (7,8), to essentially 1 (5), to values greater than 1 (3, 4).The effects of temperature are multiple and greatly complicate an analysis of this problem. It is to be expected, though little data exist for its substantiation, that the effect of temperature on rate of conduction of carbohydrate materials through petioles, will be influenced by temperature effects on numerous other processes occurring in various parts of the plant, such as respiration and assimilation, and the effect these processes have on concentration gradients between regions of export and import. Studies, therefore, in which the entire plant is subjected to different temperatures (4), although contributing much data of value, do not permit a clear analysis of the temperature effect on the process of translocation per se. In the present experiments, therefore, only the petiole temperature was varied, the rest of the plant in all treatments being maintained at a temperature of 20 ± 10 C. Materials and methodsThe report by WEINTRAUB and BROWN (6) that stem elongation of Phaseolus vulgaris var. Black Valentine was directly proportional, within the range of 0 to .75 M, to the concentration of sugar supplied to the leaves suggested that this relationship could be used as a basis of approach for studying the effect of temperature on translocation of carbohydrates. If temperature has an effect on the rate of movement of sugar through the petiole then the amount of sugar reaching the growing tip will vary with temperature and the rate of elongation should vary accordingly. Stem elongation may then be used as an index to the effect of temperature on translocation of sugar. The basic features of the method, therefore, consisted of jacketing the petiole of one primary leaf, immersing the blade in sugar solution and measuring the subsequent elongation of the plant occurring in the dark. Seeds of Phaseolus vulgaris, variety Burpee's Stringless Greenpod (in