2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 



country as compared with such studies in England, France, and 

 Germany. Cummings and Jones (2), using open cases in the green- 

 house, hberated the carbon dioxide from sodium-bicarbonate sul- 

 phuric-acid generators in such a manner that the plants were bathed 

 in an atmosphere rich in carbon dioxide for 8 hours a day. Closed 

 cases were not satisfactory, since they subjected the plants to such 

 abnormal conditions that consistent results were not obtainable. Ex- 

 periments with a rather wide variety of plants indicated a general 

 increase in plant production and that plants can use to good advantage 

 more carbon dioxide than occurs normally in air. The optimum 

 quantity of carbon dioxide, as found by these authors, for plants 

 grown in open boxes (26x18 inches and 26 inches deep for the 

 larger plants, and 52x28x12 inches for the smaller ones) varied 

 with the plant. For lettuce this quantity was about 300 liters of 

 carbon dioxide a day. Cummings and Jones further conclude that 

 the continuity of supply is as important as the total amount. 



Arthur, Guthrie, and Newell ( r), working- at the Boyce Thompson 

 Institute for Plant Research, Inc., have studied the effects on plant 

 growth and chemical composition of increased carbon-dioxide concen- 

 trations in greenhouses and in constantly conditioned rooms. The air 

 was enriched with carbon dioxide to about 0.3 percent, or 10 times that 

 of normal air. In addition to sunlight one of the greenhouses received 

 supplementary artificial light, and one of the rooms had artificial light 

 only. Several types of plants were used, the small grains being repre- 

 sented by barley, wheat, and oats. Their spring wheat (variety blue 

 stem) data are shown in table i. 



Table i. — Expcrhucntal Results on the Chemical Composition of the Aerial 

 Portion of IJ'heat [from Arthur, GutJirie, and Nezvell (/)] 



Carbohydrate (percent 

 dry weight) 



Greenhouse i received 6 hours supplementary light each night from crane. 

 Greenhouse 2 received same illumination and additional carbon dioxide. 

 24-hour day plants grown in constant-light room. 



