78 PLANT GROWTH SUBSTANCES 



terial, and that was available inexpensively, conveniently, with minimal 

 space requirements as seedlings. Such seedlings will continue to be an 

 ideal source of experimental material, and only for processes typical of 

 the mature plant, such as flowering and fruiting, will we be restricted in 

 our experimental material to mature plants. 



History is not something which abruptly ends. If I had written my 

 speech an hour ago, I would have had to include the advances made in 

 the auxin field this morning and afternoon. I think all of us this morning 

 were aware that history was being made. Something which had been 

 coming slowly, almost imperceptibly, was suddenly spotlighted. I refer 

 here to the demotion of auxin by Dr. Thimann from an executive 

 position to a simple policing job. This actually creates a number of new 

 positions to be filled, and I hope that soon not only nominations for 

 the position of Director of Root Formation, or Coordinator of Cambial 

 Activity will be made, but that in competitive experimental examina- 

 tions these positions will be filled by purified and recrystallized chemicals, 

 which will take a place of honor on the shelf of any self-respecting 

 chemist, and which will become known by some cryptic combination 

 of letters and numbers. 



REFERENCES 



1. Avery, G. S., Burkholder, P. R., and Creighton, H. B., Am. J. 



Botany, 24:51 (1937). 



2. Beijerinck, M. W., Botan. Zeit., 46:1, 17 (1888). 



3. Boysen Jensen, P., Ber. deut. botan. Ges., 28:118 (1910). 



4. , Bull. acad. roy. sci. et lettres Danemar\, No. i, 3 (191 1). 



5. Cholodny, N., Jahrb. wiss. Botan., 65:447 (1926). 



6. , Biol. Zentr., 47:604 (1927). 



7. Darwin, C, The Power of Movement in Plants (John Murray, London, 



1880). 



8. DoLK, H. E., Proc. Koninkl. Nederland Akad. Wetenschap, 29:1113 (1926). 



9. , Geotropie en ^rom/o/" (Kemink & Zoon N. V., 1930). 



10 Fitting, W., Jahrb. wiss. Botan., 44:177 (1907). 



11. , Z. Botan., 1:1 (1909). 



12. KoGL, F. and Haagen-Smit, A. J., Proc. Koninkl. Nederland AJ^ad. IVeten- 



schap, 34:1411 (1931). 



13. , and Erxleben, H., Z. physiol. Chem., 228:90 (1934). 



14. LoEB, J., Botan. Gaz., 63:25 (1917). 



15. , /. Gen. Physiol., 5:831 (1923). 



16. Paal, a., Ber. deut. botan. Ges., 32:499 (1914). 



17. , Jahrb. wiss. Botan., 58:406 (1918). 



18. Sachs, J., Botan. Zeit., 2y.iiy (1865). 



19. , Arb. Botan. Inst. Wiirzburg, 2:452, 689 (1880, 1882). 



