F. W. WENT 73 



removal of the auxin-production center, and that auxin was produced 

 again at the cut surface two and one half hours after decapitation, 

 simultaneously with a rise in growth rate of the stump. Avery et al. (i), 

 and W. Zimmermann (31) found a close parallelism between auxin 

 production by the terminal bud of woody branches and their growth 

 rate. Went and Thimann (29) found the same parallelism in the Avena 

 coleoptile. It should be stressed that all this work was carried out by 

 measuring the auxin which diffused from the tissues into agar. 



It turned out that the responses to gravity of all plants which were 

 investigated fitted excellently into the general auxin theory of tropisms. 

 The work of Dolk (9) should be mentioned here specifically. 



Thus the morphological polarity existing in the plant turned out to 

 be based on the polar transport of auxin, and a typical morphological 

 problem was brought into the realm of physiology. It seems amazing 

 that morphologists and physiologists have not made more use of this 

 common meeting ground. 



It would take too long to follow in detail all the work which was 

 carried out in the thirties. First a period of consolidation set in, when the 

 knowledge gained about auxin was extended in breadth. In numerous 

 talks and speeches my father disseminated the new knowledge, especially 

 in Europe, so that soon botanists there were auxin-conscious. In America 

 it took longer, and it was really my predecessor in Pasadena, Herman 

 Dolk, who brought the experimental attack on auxin to this country. 

 With Thimann he did pioneer work, and their first two students, James 

 Bonner and Folke Skoog, of course followed an auxin career. Yet 

 in those early days the existence of auxin was still questioned by many 

 otherwise well-informed scientists. Then it was almost an adventure 

 to give a talk on auxin before a botanical audience; the reactions 

 ran the whole gamut from enthusiastic acceptance to disdainful rejection. 

 It is remr.rkable to observe here, how this situation has changed in the 

 last fifteen years. 



Gradually a differentiation in the research on auxin set in. Originally 

 the main emphasis had been laid on a study of its biological and physio- 

 logical role, its function as correlation carrier, as chemical messenger. 

 This research had opened remarkable vistas of the whole regulation of 

 plant growth; it had shown that a single agent, auxin, tied together a 

 large number of activities inside the plant. It had become clear that the 

 effects of stem tip and young developing leaves on stem elongation were 



