EFFECTS OF GIBBERELLIN 379 



elongation phenomena we now know are characteristic of gibberellin, 

 but could not then be chemically identified when extraction and assay 

 procedures for auxin were followed. A fruitful area for research should 

 lie in a study of the comparative flower-inducing effects of the various 

 gibberellins and "gibberellin-like" substances derived from the de- 

 veloping floral structures and immature seeds of higher plants (Phm- 

 ney et ai, 1957). Emphasis on the extraction of the hypothetical 

 flower-inducing hormone from the developing reproductive organs of 

 plants may yet yield convincing evidence of its existence in these 

 structures, whereas attempts to obtain a similar substance from photo- 

 induced leaves have consistently failed. 



REFERENCES 



Bukovac, M. J., and S. H. Wittwer. 1957. Gibberellin and higher plants. II. 



Induction of flowering in biennials. Mich. Agr. Expt. Sta. Quart. Bull., 39, 



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 Bukovac, M. J., and S. H. Wittwer. 1958. Reproductive responses of lettuce 



{Lactuca sativa, variety Great Lakes) to gibberellin as influenced by seed 



vernalization, photoperiod and temperature. Proc. Am. Soc. Hort. Sci., 71, 



407-11. 

 Bunsow, R., and R. Harder. 1956a. Blutenbildung von Bryophyllum durch 



Gibberellin. Natunvissenschaften, 43, 479-80. 

 . 1956b. Blutenbildung von Lampsana durch Gibberellin. Naturwissen- 



schaften, 43, 527. 



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 Carr, D. J., A. J. McComb, and L. D. Osborne. 1957. Replacement of the 



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Naturwissenschaften, 44, ASA. 

 Lang, A. 1956a. Induction of flower formation in biennial Hyoscyamus by 



treatment with gibberellin. Naturwissenschaften, 43, 284-85. 

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544. 



1957. The effect of gibberellin upon flower formation. Proc. Natl. 



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