J. M. BEAL 165 



the tissues correlated with aging, plays a major role in the type and 

 quantity of response. 



7. It is as important to know the qualities of the tissues that are 

 to respond as it is to know the growth substance to be employed, since 

 to many of the substances the responses are very similar while to others 

 they may be quite different, as for example to naphthaleneacetic acid 

 and naphthylacetamide. Thus the growth-regulating substance can be 

 regarded only as a releaser (or in part a controlling means) of response 

 of the living cell, which still remains the critical entity, and not as the 

 prime inciter itself. 



8. While in morphogenetic studies genetic capacity may control, yet 

 growth-regulating substances determine the degree to which expression 

 does or may take place. They are one of a complex group of factors, in- 

 cluding light, temperature, food and nutrient supply, and other envi- 

 ronmental conditions. Therefore growth regulator or Ergocrine is a 

 more precise use of terminology than growth substance or even hor- 

 mone, because many of the effects of these substances suppress certain 

 physiological reactions as well as excite them. The same is true for the 

 morphological responses and final visible changes as well. 



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3. Beal, J. M., Botan. Gaz., 99:881 (1938). 



4. , ibid., 105:25 (1943)- 



5. , ibid., 107:217 (1945). 



6. , ibid., 108:166 (1946). 



7. BoRTHwicK, H. A., Hamner, K. C, and Parker, M. W., ibid., 98:491 



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8. BoYSEN Jensen, P., Avery, G. S., and Burkholder, P. R., Growth 



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