CHLOROPHYLL AND GROWTH 



131 



were brought into diffuselight with gradually 

 increasing intensity, the normal appearance 



was fi- 

 nally 

 resum- 

 ed. The 

 color of 

 the eti- 

 olated 

 leaves was of the cus- 

 tomary waxy yellow, 

 upon which the reddish pur- 

 ple color areas characteris- 

 tic of the external tissue 

 were boldly apparent. The 

 spathe exhibited great vari- 

 ety of reaction, but in gen- 

 eral it did not attain full 

 development. This was 

 the invariable result if this 

 member alone was enclosed 

 in a covering excluding 

 light. And although not 

 ' responsive to the directive 

 action of light or gravity, 

 it assumed an upright or 

 FiG.i4.-Aris^matri-0^^wardly rccurvcd posi- 



phyllum grown in an at- -(-ion iu darknCSS. 

 mospnere free from car- 

 bon dioxide. If plants with mature 



leaves were placed in the dark chamber a re- 



