Jan., 1923] BAKKE AND ERDMAN-CULTURES OF MARQUIS WHEAT 
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The approach toward neutrality is more striking for the sand cultures than 
it is for the solution cultures. This statement is particularly true of the 
control solutions. In the control water cultures the reaction had changed 
after 3J days to the extent of 1.0 pH toward neutrality, whereas in the sand 
cultures it changed from 4.4 pH to 6.38 pH, or a decrease in acidity of 2.0 
pH. These data would seem to lend support to the adsorption theory, in 
that the sand particles apparently have adsorbed sufficient anions from 
the solutions to cause these differences in pH values, and hence favor greater 
root development in the sand cultures. The water cultures giving the 
greatest dry weight of tops and of roots have pH values ranging from 5.90 
to 7.20. The sand cultures having the largest total dry weight of tops and 
of roots have pH values ranging from 5.98 to 6.88. However, an examination 
of these data in table 4 shows no correlation between total yield of dry 
matter and the hydrogen-ion concentration. 
Summary and Conclusions 
The work reported in this paper has offered a means of comparison of 
sand and water cultures of Marquis wheat when grown in nutrient solutions 
of type III. Each series of solutions contained 21 cultures of different salt 
proportions, varied in increments of i and all having a total osmotic 
concentration value of 1.00 atmosphere. The salts used were KN 0 3 , 
Ca(H 2 P 0 4 ) 2 , and MgS 0 4 , together with a “trace” of FeP 0 4 . The main 
conclusions to be drawn from this study are as follows: 
1. The solutions producing the maximum yield of tops for the sand 
and water cultures showed marked variations in salt proportions. The 
“best” water-culture solution (R2S1) was characterized by having two 
eighths of its total osmotic concentration derived from KN 0 3 ; one eighth 
from Ca(H 2 P 0 4 ) 2 ; and five eighths from MgS 0 4 . The “best” sand-culture 
solution (R3S3) had three eighths of its total osmotic concentration due to 
KN 0 3 ; three eighths to Ca(H 2 P 0 4 ) 2 ; and two eighths to MgS 0 4 . 
2. The high-yielding water culture R2S1 was far superior to that in 
Shive’s R5C2 solution. The high-yielding sand culture also gave much 
greater production than the control solution. 
3. The largest amount of absorption and the maximum green and dry 
weight of tops favored the water cultures. The greatest root development 
was obtained from the sand cultures. 
4. In general, those cultures having the greatest transpiration for the 
entire growth period also showed the greatest dry weight of tops and of 
roots. 
5. The reaction of the medium in which the plants were grown changed 
from an average acidity of pH 3.75 before growing the wheat cultures, to 
an average acidity of pH 5.94 for the water cultures, and to pH 6.66 for 
the sand cultures, after growing the plants for one 3^-day period. No 
