424 



B. B. Stowe 



considerable accentuation of section growth over that achieved 

 with lAA plus GA3 alone. The concentrations of vitamin E and 

 methyl linoleate employed, although higher by 6 to 30 times that of 

 lAA, still may be considered to lie within a hormonal range. 



Further examination of the data of Table 3 reveals that the 

 lipides are completely ineffective in the absence of an auxin (other 

 tests have shown that 1-naphthaleneacetic acid and 2,4-dichIorophen- 

 oxyacetic acid are also capable of potentiating the lipide response). 

 A small promotion of gibberellic acid action is frequently found, but 

 has never reached the level of statistical significance. The enhance- 

 ment of auxin-induced growth is unmistakable, but it is in the 

 presence of both auxin and gibberellic acid that the greatest margin 

 of significance is attained. Hence it appears that the lipides act 

 hormonally, as synergists of the action of auxins and, in the presence 

 of an auxin, of gibberellic acid. Any explanation of the lipide effect 

 thus must be linked to the actions of these hormones. 



Although the evidence is still far from conclusive, we have ad- 



Table 4. Comparison of effectiveness of different lipides in enhancing auxin- 

 induced growth of sections of 'Laxton's Progress' pea epicotyls with their ability to 

 restore cytochrome activity of isooctane extracted animal particulate preparations 



(17). 



♦Data of (16). 



t Compiled from data in (5, 7, 



23). 



