IV 



CHEMISTRY OF THE GROWTH SUBSTANCES 



765 



analysis, that the antagonism is competitive {cf. section VI lb). In other cases, e.g. 

 cyclohexaneacetic acid, XXI, or 2,3,5-triiodobenzoic acid, XXII, they act as 



CH, 



I -^ 



■C— COOH 



I 



COOH 

 I 

 CH 



HoC C-Hp 



i I 

 H2 



2,4,6-Trichlorophenoxy a-Indoleisobutyric Cyclohexaneacetic 

 acetic acid acid acid 



XIX XX XXI 



2,3,5-Triiodo- 



benzoic acid 



XXII 



ERRATUM 



Chapter 10, page 765. The formula XXI should read 



COOH 

 CHa 



H2C ^CH2 



^2C^^/CH2 



Ha 



Cyclohexaneacetic 

 acid 

 XXI 



while gibberellin A2 of Sumiki and co-workers is 



CjpHjgOg. 



The crystalline 



product obtained from cultures oi Fusarium nioniliforme in the USA is a mixture 

 of Aj and A3 (Stodola et al., 1955). The original "gibberelhn A", first isolated 

 by Yabuta and Hayashi (1939) niay have contained all three. So far as their 

 potencies have been compared all three seem to be about equally active, but 

 as yet the comparisons arc very incomplete. On the other hand the breakdown 

 product allogibberic acid, (gibberellin B of Sumiki) XXIV, C18H20O3, may have 

 lower activity, while its rearrangement product formed in hot dilute acid, gibberic 

 acid, XXV, is apparently inactive. A3 has also been isolated from higher plants. 



Allogibberic acid 

 XXIV 



. , CH2 CO 



'-^3 H COOH 



Gibberic acid 

 XXV 



Literature p. 8i6 



