Tue Carson DIOXIDE OF THE Sort AIR a 388; 
tables and plotted in the curves are for the period of ten weeks during 
which the plants were growing most actively. Before and after this 
period no relationship was found to exist between the amount of water 
transpired and the carbon dioxide produced by the plants. 
Ter cent Panne 
of CO2 4 of water 
eoeeore 
CLO CNIS 
3C 
SCOCC COC OC OR BR HR RP HR RP eR RN NN HW WL 
bee DO OOH OF MD IDO ORM WH ROD AITWAWOORN WH OID 
i 
> 
Voter rrarssp1red —— > 10 
i. 3 b 
Corbor7 Hoxvde ------ (2 
2 v 
March /pril May 
Fic. 49. RELATION BETWEEN WATER TRANSPIRED AND CARBON DIOXIDE PRODUCED 
BY AN OAT CROP FOR THE TEN WEEKS DURING WHICH ITS GROWTH WAS MOST VIG- 
orous, 1918 
It is seen in columns G and H of tables 3 and 4 that the percentage of 
carbon dioxide produced to each pound of water transpired, approaches 
a constant much more nearly when the carbon dioxide in the uncropped 
soil is subtracted from that in the cropped soil. The smaller coefficients 
of variability of 22.5 + 3.74 as compared with 37.4 + 5.65 in 1917, and 
15.1 + 2.32 as against 19.17 + 3.12 in 1918, bring out this fact fairly 
clearly. If it is assumed that the amount of carbon dioxide produced 
and the amount of water transpired are indications of life activity, then 
the relationships found between the carbon dioxide in the soil, and the 
water transpired, would hold only when the carbon dioxide is produced 
