236 



CHEMICAL AGENTS AND GROWTH 



Fig. 9. Histograms giving the biological activity (on coleoptile seg- 

 ments) of 1-cm sections of paper strips. On these strips had been chromat- 

 ographed the extracts of Cornus florida rubra grown under long days 

 (top) and short days (bottom). The black bars represent the average 

 growth (10 replicates each) over the controls (dotted lines), the white 

 bars the average growth below the controls. Extracts: 0.61 and 0.66 g 

 fresh weight, respectively, of tips of branches extracted 5 times at 0°C 

 with ethylacetate. Extracts evaporated to dryness, taken back into 

 ether and chromatographed on Whatman 3 MM paper in isopropanol 

 (80) + ammonia (10) + water (10) (V/V). The positions of indole- 

 acetic acid (A), indoleacetonitrile (N), and ethylindoleacetate (E) have 

 been indicated (from Waxman, 1957). 



