June, 1922] 



MUENSCHER — ABSORPTION OF SALTS 



323 



It is true that the concentration of the solution used in the winter series was 

 only one half as great as in the summer series. The question might be 

 raised as to whether in this case the dilute solution, rather than shading, 

 might cause the increase in water requirement. The following experiment 

 shows that this is not the case. 



Dilute-Concentrated Solution Cultures 



Table 6 compares the data of the cultures grown in a concentrated solu- 

 tion with similar cultures grown in a dilute soulution under the same illu- 

 mination. The plants grown in a dilute solution have slightly higher actual 

 green weight, dry weight, and ash weight than those grown in the concen- 

 trated solution. It is possible that a concentration of 0.28 percent may 

 have been somewhat injurious to barley. The plants grown in a concen- 

 trated solution have even a slightly higher water requirement and use a 

 greater quantity of water per gram of ash in the winter than the plants 

 grown in a dilute solution in the summer. It appears, therefore, that the 

 reduced sunlight rather than the reduced concentration of the solution is 

 largely responsible for the increased water requirement in the cultures of the 

 winter series, even if the actual transpiration is decreased considerably by 

 shading. 



Table 6. Relation of Ash Content in Barley Plants to the Amount of Transpiration as 



Affected by a Difference in Concentration of Nutrient Solution. Winter 



Series. Plants Grown 5 Weeks {January iq to February 24, iq2i) 



No. of cultures averaged . . . 



Green weight per culture (grams) 



Dry weight per culture (grams) . 



Total ash content per culture 

 (grams) 



Ash content (percentage of green 

 weight) 



Ash content (percentage of dry- 

 weight) 



Total water trsinspired (cc.) .... 



Water used per gram dry matter 

 (cc.) 



Water used per gram ash content 

 (cc.) 



Table 7 presents the percentages of ash in the tops, roots, and total 

 plants expressed as percentages of dry weight and green weight for all cul- 

 tures grown under the various conditions of the winter series. When these 

 data are compared with the data from the summer series in tables 3 and 4, 

 it will be noted that the percentage of ash expressed as percentage of dry 

 weight usually varies less than five percent between the high and low trans- 



