An anatomical investigation was made about the difference in length in two varieties of Pisum sativum, , „slender pea” („rankerwt”) and „white raisin” (witrozijn”). The greater length of „slender pea” is due to more internodes and more and longer cells. Production of growth substance of „slender pea” as well as of „white raisin” depends on the time during which their tips were on the agar plates. Production of auxin, put down in a graph, shöws for both types an optimum curve as far as time is considered. The growth substance which has diffused into the agar, is inactivated by oxidizing enzymes. In „slender pea” destruction is less effective than in „white raisin”. After hours there is about twice as much auxin present in „slender pea” than in „white raisin”. The cells of „slender pea” are more extensible in the stretching zone than those of „white raisin”. This can be explained by a stronger production of auxin. Morever, in „slender pea” the growth substance is present in lower zones of the stem, whose stretching zone is longer than that of „white raisin”. This makes it probable that in „slender pea” the inactivation also takes place in lower parts of the stem or at least takes the upperhand there. Osmotic values of the cells in the stretching zone are the same for both varieties. Tips of „white raisin” contain more catalase than those of „slender pea”; this explains the more effective destruction of the auxin in ,white raisin”. If we consider the relative data for length of cells, number of cells, extensibility of the cell walls and the amount of catalase, it appears that they are all of the same order of magnitude, as can be seen in table X. The relative data for lengths of internodes are of course greater, as the length of an internode is determined by length X number of cells. It may be concluded that the cell stretching of „slender pea” and „white raisin” is finally determined by their amount of oxidizing enzymes. This research was started in the Botanical Laboratory of the State University of Groningen, Netherlands, and was continued in the Botanical Institute of the State University of Ghent, Belgium. We wish to express our thanks to the director of this Institute, Dr. G. L. Funke, for his interest and for the translation of the text.