Smithsonian Report, 1936. — Johnston 



Plate 3 



1. General api'iMimur -i ■ i;t;a pints. TLat in !lie (')ic:-;iijun'_l was upfii to u,)rnial all-, the two in the 

 background were euL'losed in glass. Carbon dioxide was added to the one on the right. 



2. General appearance of wheat at harvest. Average carbon-dioxide concentrations relative to air were 



A, 3.8; B, 1.1; C, 0.9. 



