36 J. A. Bentley 



they occur largely in the acid fractions. There is, however, a growing 

 body of evidence on the occurrence of neutral auxins [e.g., Fukui et al. 

 (4, 5), on a neutral auxin in immature corn kernels and in corn pollen]. 

 The neutral ether and neutral saponified aqueous fractions of Ocli- 

 romonas 1 were inactive when chromatographed in isopropanol-am- 

 monia. The neutral ether fraction of Ochromonas 2, however, after 

 preliminary chromatography in water, showed a well-marked zone of 

 activity on chromatography in isopropanol-ammonia (Figure 6.A). 

 The neutral saponified aqueous fraction showed slight inhibition 

 along the length of the paper (Figure 6B), but since it was thought 

 that this might be due to something toxic, the chromatogram was 

 eluted in two portions and rechromatographed (Rf 0.8 to 1.0 in Figure 

 6C; Rf to 0.8 in Figure 6D). Surprisingly, considerable activity was 

 located, again in zone Z, with hints of activity in zones X and Y. 

 Either something inhibitory is preventing the activity from showing 

 in Figure 6B, or else there are inactive precinsors on the paper, which 

 release the active compounds X, Y, and Z on further manipulation 

 and chromatography of the extracts. The appearance of these com- 

 pounds in the neutral fractions may be due to incomplete separation 

 from the acidic fraction, or possibly a precursor of X, Y, and Z may 

 be neutral or amphoteric. In any event, the active compounds occur 

 in much smaller amounts in the neutral fractions than in the acid 

 fraction. For example, no activity could be obtained from the orig- 

 inal base lines on second chromatography in ^vater, whereas in acid 

 fractions it often can. 



DISCUSSION 



The foregoing results establish that a number of algae, covering 

 several classes, contain biologically active substances with activity 

 similar to the auxins of the higher plants. The main bulk of the ac- 

 tivity is located in two zones, which have been called zones X and Z, 

 although these zones do not necessarily represent the same substances 

 in all the species examined. Zone X runs usually at an Rf of approx- 

 imately 0.3 to 0.5, and Z at Rf approximately 0.9, in ammoniacal iso- 

 propanol. The activity in the ether extracts of saponified fractions 

 indicates that there are water-soluble, ether-insoluble auxin precur- 

 sors in the algae. Hiesc ether-insoluble compounds yield ether-solu- 

 ble auxins on treatment with alkali. Under the conditions chosen, 

 bioassay has shown that no ether-soluble auxins are produced from 

 tryptophan. It is possible that the active compounds located in the 

 saponified fractions arc the same substances as the ether-soluble aux- 

 ins present in (he algae originally (the acidic ether fractions), as both 

 sets .show a similar mutual interconvertibility. It is possible that X and 



