802 A. S. Crafts 



inal compound. Now with lAA I must admit that I have no idea 

 what it is that's moving, but we hope eventually that we can find out. 

 I suspect it may be a conjugate. 



Dr. Thimann: Could you say why you are convinced that radio- 

 activity in the 2,4-D autograms represents unchanged 2,4-D? 



Dr. Crafts: My conclusions are based on several observations and 

 on Dr. Weintraub's work showing that the decarboxylation of 2,4-D 

 goes on at a relatively slow pace. We can also extract these com- 

 pounds from the roots and get bud suppression and leaf deformation 

 typical of 2,4-D. We are now engaged in chromatographing the ex- 

 tracts of these and hope to follow this much further. 



Professor Blackman: We have heard a good deal about the effects 

 of surfactants per se. Perhaps I might point out that if you take a series 

 of different types of wetting agents and increase the concentration 

 past the point where there is any further and appreciable lowering 

 of the surface tension of water then, though the surface tension is 

 not changed, there will still be effects of concentration on the level of 

 retention following a spray application. Moreover there will be sig- 

 nificant interactions between the species and the type of surfactant. 

 One of the many queries that arise is whether measurements of sur- 

 face tension by accepted methods employing static conditions are ap- 

 plicable to droplets impinging on the leaf surface. 



