1918] NOYES, TROST, & YODER—ROOT VARIATIONS 371 
Carbon dioxide gas additions to the soil did not prevent the roots 
from penetrating deeply, for in all pots the roots penetrated to the 
bottom. It was noted that roots grew to very near the openings 
ore — 
pea 
Fic. 6.—Best 3 Lactuca sativa of 9 under comparison: pot at left received no 
carbon dioxide, one in middle 8 hours daily, one at right constant treatment of carbon 
dioxide 
2 at left no carbon dioxide treat- 
7, 2 at right constant treat- 
Fic. 7,—Representativ e roots of Lactuca sativi 
ments, 2 in middle 8 hours’ carbon dioxide treatment daily, 
ment with carbon dioxide. 
where the carbon dioxide gas entered the pots. The gas had an 
effect on the development of the roots of the bean plant that was 
different from that observed with any other plant tested. The 
