Scientific Results 



Altogether eight compounds were found by Zimmerman 

 and Wilcoxon (1935) to cause unusual activity such as nastic 

 responses, root-initiation, etc., when applied to sizeable 

 plants; the list has been lengthened since. 



Initiation of Roots 



All the compounds mentioned in the preceding section, and 

 also anthracene-acetic, fluorene-acetic, and acenaphthene- 

 acetic acids, caused local initiation of roots (adventitious roots) 

 on aerial parts of growing plants of tomato, sunflower, 

 African marigold, Jerusalem artichoke, tobacco, dahlia, and 

 buckwheat, a-naphthyl-acetic and indole-butyric acids were 

 especially effective in initiating roots on stems and leaves. 

 The subjoined table, taken from the paper by Zimmerman 

 and Wilcoxon (Contrib. Boyce Thompson Institute, 1935, 7, 

 211), indicates the approximate effective concentration ranges 

 of five of the substances, expressed as percentages in lanolin. 

 Numerical results are, of course, affected by the mode of 

 application, the species of plant, and the type of effect sought. 



Table — Effective Concentration Ranges of Five 

 Synthetic Growth- Substances for Tomato, ex- 

 pressed IN Percentages in Lanolin. 



This remarkable initiation of roots is well shown by 

 Figs, z and 3, taken by permission from the paper by Zim- 



29 



B2 



