76 PLANT GROWTH SUBSTANCES 



exhaustive extraction became a fad and was in no way correlated any 

 more with the physiological role of auxin. From all we know about 

 indoleacetic acid and its formation from, for instance, tryptophan, we 

 can easily see that under certain circumstances large amounts of indole- 

 acetic acid could be released from tryptophan by way of protein break- 

 down, which during the life of the tissue never would have been available. 

 I would like to urge not the abandoning of different extraction methods, 

 but their simultaneous use coupled with a physiological analysis. Thus 

 it may be possible to find for each process a form of auxin or a fraction 

 with which it is correlated. In this way it may be possible to make some 

 sense of the enormous amount of experimental data which are amassing. 



Let me make clear what I wanted to say with a simile. Suppose that 

 we want to find the role of water in a steamship. By judicious experi- 

 ments we can find that a certain amount of fresh water is necessary for 

 steam generation, and sea water is needed for cooling purposes. Such 

 experiments would be physiological (for example, plugging the supply 

 line for cooling water, excision and regrafting of fresh water tanks and 

 so on) . A biochemical study of the steamship would presumably start with 

 sectioning of the ship into segments and squeezing each. Some sections 

 would yield large amounts of water (those containing the fresh water 

 tanks and ballast tanks), others would have intermediate amounts, such 

 as the boiler room, and again others would yield almost no water, such 

 as the turbine room. Only by judicious separation of water from boilers, 

 steam from turbines, and storage tank water could such a biochemical 

 analysis of the steamship yield intelligible results. Total extraction of 

 water would not give any correlations with the functions of the steam- 

 ship. 



The development of the auxin field is a typical example of how science 

 works. Originally growth of a plant was considered almost as a category, 

 in the way the Greeks considered water, fire, or earth. It was taken as a 

 property of the living organism. When it turned out that in the absence 

 of auxin there was no growth, and that stem growth could be controlled 

 at will by the application of measured amounts of auxin, it seemed to 

 many that we had an explanation of growth. This was partly because 

 some of the mystic quality of growth was possessed by a relatively 

 simple substance which could be stored in crystalline form on the 

 chemical shelf of the laboratory. Some of my more mystically inchned 

 friends actually disapproved of the idea of an unromantic chemical 



