“…I t is difficult to see how pet:meability changes by them selves, as suggested by Pohl (66) and others, can be considered to be the primary cause, since here only rates are affected, and permeability to water is already relatively great. In a recent review, Audus (67) concludes that we must either explain a number of separate effects produced by auxin in different tissues, or we must base our theory on some more fundamental action, or "master reaction" in the sense of Thimann (68). Northen's (69) report of dissociation of protoplasmic proteins by auxin is given as an example.…”