When 14CO2 was applied to the leafy shoot of a stem segment, the xylem of which was perfused with distilled water, a proportion of the activity was detected in the xylem exudate, mainly in the form of sucrose. Experiments in which 36Rb, 22Na, or 32P-phosphate were applied to the cambial surface of a raised portion of bark revealed that these solutes could also pass into the xylem exudate. With the ions, the amount which moved into the xylem vessels was dependent upon the time of year at which the experiments were performed.