The Development of the Graft Union

In this paper a new method is described for the examination of graft formation. The method depends in principle on the measurement of the tensile strength of the graft at intervals of 2 days. It has been applied to the analysis of the development of a simple graft, made by cutting across an internode of a tomato seedling and rejoining the separated portions. The method requires that the treatment be applied to a group of a hundred seedlings from which samples are taken at intervals of 2 days. With this general technique and with the system used it has been shown that the development of the graft continues steadily after the second day of the experiment, that graft formation is most rapid when the different tissues of the stem coincide in the stock and the scion, and that the tensile strength of the graft is reduced markedly when the turgidity of the tissues is depressed. In the last section of the paper the significance of these several observations is discussed.