CHLOROPHYLL AND GROWTH 13' 



tion of a primary root more than a meter in 

 length, before the unfolding of the first foliage 

 leaf in the natural habitat of the plant. In 

 planting the seeds in moist soil this excessive 

 development of the roots was useless, and 

 foliage leaves began to unfold when the root 

 had attained a length of a few centimeters. 



The seedlings grown in small pots were 

 placed inside the apparatus and kept free from ^ i. 

 carbon dioxide for a period of thirty to forty ^[^^ Phoenix 

 days. The leaves, which at the beginning of 

 the experiment were emerging from the sheath- 

 ing scale, exposing a tip one to two centi- 

 meters in length, attained a length of fifteen 

 centimeters and a complete normal expansion 

 corresponding to that of organs grown in the 

 open air. Such leaves usually attain a length 

 of twenty to thirty centimeters by a slow 

 process of growth lasting several months, and 

 my experiment, therefore, covers only the 

 earlier stages of development. 



Specimens placed in a dark chamber during 

 a period of thirty to forty days exhibited an 

 exaggerated elongation of the cotyledonary 

 and leaf scales, as well as the leaf itself, which 

 retained its lamina in the plicately folded 

 position. The increase in length amounted 

 to twenty to thirty per cent more than in 

 control plants. 



It is safe to conclude that the development 



