Feb., 1922] 
ARNDT THE GROWTH OF FIELD CORN 
59 
(b) Sand Cultures. The plants in the sand cultures were grown for 
40 days in April and May. The modifications of solution "H" and the 
C H'S H'/y H-c Ttts F-N F~C /IS /f-zv/f-c 
Fig, 5. Relative growth of tops and roots, transpiration, and the H-ion concentration 
before and after growth in solution " H " upon the addition of 0.0004 ^ ^cid and salts. For 
notation see figure 4. 
results are given in table 5. The transpiration is reported for the last 16 
days of growth. The total average loss by evaporation from the pots with- 
out plants, which was deducted from the total loss of the others to determine 
the amount lost by transpiration, was 405 cc. During the period of growth 
the average daily loss from the white and black atmometers was 7.83 cc. 
and 8.5 cc. respectively. The small difference between these values is 
due to the fact that the plants were grown in a well shaded greenhouse and 
to the large proportion of cloudy weather during the first part of the ex- 
periment. On sunny days the temperature ranged from 30° C. to 35° C. 
This was probably too high for the optimum growth of corn. The pH 
values are given for the first 50 cc. and for the total 500 cc. drawn off at the 
end of the second week, and also at the time of the last renewal for which 
the pH value of the last 50 cc. is also given. The change in the pH values 
of the initial solutions by plant growth was much greater in the sand cultures 
than in the solution cultures, as is well shown in figure 6. The depression 
of growth of the tops is also on an average less, and particularly so in case 
