In recent years the literature has contained numerous investigations on the rate of growth. These have ranged from studies on the rate of growth of the dairy cow to bacteria. Increase in length, breadth, and weight have all been used as criteria of growth. Among these investigations there is no mention of the growth of fruits. In fact, as far as the writer is aware, only one single experiment has ever been published in which the growth of a fruit was measured throughout the growth period.1 This was an experiment by Anderson (1) in 1895 on the fruit of Cucurbit a Pepo, in which weight was measured by a self registering balance. The growth of fruits is somewhat different from that of other plant organs, being mainly a storing up process, and for this reason it has been thought worth while to investigate their growth, also. In the summer of 1924 preliminary studies of the growth of fruits were commenced. The intention in the beginning was to measure growth of individual fruits by weighing them on the plant at intervals of a week during the growing season. To do this it would be necessary to select easily grown fruits of considerable size, with long and flexible peduncles. The plants finally selected were: Cucurbit a Pepo var. coTvdensa (scalloped summer squash), Cucumis Melo (muskmelon), C. sativus (cucumber), and Lycopersicum esculentum (tomato). It soon became obvious that it would not be feasible to measure growth by the increase in weight of fruits on the vines. Therefore another method was developed, namely the measurement of the volume of a fruit by the displacement of water in a calibrated container. By this method the increase in growth, as represented by increase in volume, could be measured fairly rapidly and accurately with the least disturbance of the plant and without injuring the fruit. The first measurement was made at the time when the blossoms had just appeared. At this time the young fruits (ovaries) differed somewhat in size, but physiologically they were of the same age. In the case of the tomato it was necessary to obtain an average volume of the ovary by collecting a large number (200 to 400) from flowers