344 GROWTH FACTORS AND FLOWERING 



was able to obtain at least a good indication in a somewhat devious 

 manner. Gibberellin-like materials have been found in other seed 

 plants (Phinney et ai, 1957, and others), and we applied one such 

 gibberellin-like material, contained in the endosperm of a wild 

 cucurbit, Echinocystis macrocarpa, to a vegetative long-day plant and 

 obtained an entirely similar response as with the Fusarium gibberellins 

 (Lang et al, 1957; see Fig. 3). This result suggests that gibberellin- 



FiG. 3. Induction of flower formation in short-day-grown Somolus 

 parviflonis by endosperm of Echinocystis macrocarpa (left) and by gib- 

 berellin (right). 



like native materials are capable of regulating flower formation in 

 certain plants, specifically, that they can overcome the flower-prevent- 

 ing effect of short day in long-day plants. 



Another piece of evidence suggesting that gibberellins are involved 

 in the natural regulation of flower formation is that it seems possible 

 to enhance the effect of suboptimal photoinduction in long-day plants 

 with suboptimal gibberellin dosages, or vice versa. Some such informa- 

 tion has just been published by Biinsow and Harder (1957) for two 

 species of Rudbeckia, and I am presently in the process of gathering 

 what seem to be similar data. I should like to say, however, that these 

 data are not yet sufficient for a conclusive statement, and I am 

 mentioning them here subject to change without notice. 



The next question wiU logically be: What precisely is the role of 



