Interconvertible Naturally Occurring Auxins 27 



tions (10 mm.) with only 1 ml. of test solution in 3.5 cm. petri dishes, 

 instead of 10 ml. in 5 cm. petri dishes, as used previously. Under 

 these conditions, best growth is obtained with the addition of 1 per 

 cent sucrose and phosphate-citrate buffer (10- M K2HPO4 and 0.5 

 X 10- M citric acid at pH 5.0. With these modifications, the sensi- 

 tivity of the test can be increased 10 to 100-fold over that previously 

 obtained. 



RESULTS 



Oscillatoria spp. 



Chromatography and bioassay of the acidic ether fraction showed 

 clear-cut activity in two zones, which have been called zones X and Z 

 (Figure lA). These zones are still clearly defined even on diluting the 

 extracts 10 times. There is a spot giving a purple Ehrlich, pink Sal- 

 kowski, and pink nitrous-nitric acid reaction in zone Z. When zone 

 X is eluted and rechromatographed in either alkaline or neutral 

 conditions [?i-butanol-ethanol-1.5 N NH3 (6:2:2) or water. Figures IB 

 and IC, respectively], zone Z appears in addition to X. There is also 

 evidence of an intermediate zone (Y) in Figure IB. This nomencla- 

 ture of the zones is considered further in the discussion. Similarly, 

 when Z is eluted and rechromatographed in isopropanol-ammonia, X 

 appears (Figure ID). Thus, a mutual interconvertibility between X 

 and Z can be demonstrated, similar to the interconvertibility demon- 

 strated in tomato roots (3) and pea roots (1). It should be noted that 

 the conversion of one zone to the other is never complete — both 

 zones can be picked up on the paper and there appears to be an equi- 

 librium between them. Zone Y is more transient in the algae and 

 not so easily demonstrated. 



Chlorella pyrenoidosa 



All fractions received preliminary purification by chromatography 

 in water, and rejection of the pigment zone. 



Color tests of the acidic ether fraction chromatographed in iso- 

 propanol-ammonia gave a spot with unusual color reactions, a rapid 

 dark-blue Ehrlich reaction and faint yellow nitrous-nitric acid re- 

 action, at Rf approximately 0.8. This spot, which is also found in 

 corresponding fractions of dried Chlorella, is referred to in the dis- 

 cussion as Chlorella 5. Solutions from this zone rechromatographed 

 after bioassay gave a faint pink Ehrlich reaction in the same region. 



Bioassay of the acidic ether fraction after chromatography in iso- 

 propanol-ammonia showed that there was activity in this region and 

 also in the lAA region (Figure 2A). Rechromatography of zone Z in 



