ZIMMERMAN: FORMATIVE INFLUENCES 115 



With still other species young tissue does not respond to chemical treatment 

 whereas older tissue is susceptible. Many other illustrations could be given to 

 indicate that there are complex internal and external influences playing upon 

 the living protoplasm and that the sum total of these regulates the growth and 

 development of the plant. 



SUMMARY 



"Formative influence" as used in this report is defined and distinguished 

 from other hormone-like influences. 



For the study of formative influences three groups of compounds, ^-naph- 

 thoxy, substituted phenoxy derivatives of the lower fatty acids, and substituted 

 benzoic acids, stand out above all others. Substitutions in the nucleus of the 

 molecule may be made with halogens, amino, nitro, or methyl groups. These 

 may be used separately or in combination. Physiological activity depends upon 

 the kind, number, and position of the substituted groups. The molecular con- 

 figuration as a whole rather than any one part of the molecule appeared to 

 determine the activity. 



Characteristic responses induced with these growth regulators are illus- 

 trated in four different figures. Attention is called to the similarities between 

 responses induced with synthetic growth regulators and naturally occurring 

 virus diseases. 



BoYCE Thompson Institute for Plant Research, Inc. 

 YONKERS 3, N. Y. 



Literature Cited 



1. Boysen-Jensen, p. La transmission de I'irritation phototropique dans I'Avcna. Kgl. 

 Danske Videnskab. Selskabs. Forhandl. 1911 (1) : 3-24. 



2. Sinnott, E. W. The problem of internal dififerentiation in plants. Amer. Nat. 76: 253- 

 268. 1942. 



3. ZiAi merman, p. W. Formative influences of growth substances on plants. Cold Spring 

 Harbor Symposia on Quan. Biol. 10: 152-157. 1942. 



4. . Present status of "plant hormones." Indus. & Eng. Chem. 35: 596-601. 1943. 



{Also in Boyce Thompson Inst. Prof. Pap. 1 (35) : 307-320. 1943.) 



5. Zimmerman, P. W., and A. E. Hitchcock. Formative effects induced with /3-naph- 

 thoxyacetic acid. Contrib. Boyce Thompson Inst. 12: 1-14. 1941. 



6. . Qualitative differences in capacity of growth substances to induce formative 



effects. Amer. Jour. Bot. 28: 14s. 1941. 



7. . Substituted phenoxy and benzoic acid growth substances and the relation of 



structure to physiological activity. Contrib. Boyce Thompson Inst. 12: 321-343. 1942. 



8. . Flowering habit and correlation of organs modified by triiodobenzoic acid. Con- 

 trib. Boyce Thompson Inst. 12: 491-496. 1942. 



