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[Vol. ioj 
tions renewed intermittently had no apparent influence upon the growth of 
soybean tops, but it produced considerable increase in root development. 
3. Aeration of solution or sand cultures with continuous solution re¬ 
newal produced a marked increase in the growth of both tops and roots of 
soybeans. 
4. Continuous renewal of the nutrient solution did not alone maintain 
the supply of dissolved oxygen necessary for maximum development of the 
plants. 
5. The response of roots to aeration was much more pronounced in the 
cultures in which the solutions were continuously renewed than it was in 
those in which the solutions were only intermittently renewed. 
6. The superiority of roots grown in the aerated media over those grown 
in the non-aerated was manifested not so much in higher yield weights as in 
the development of very efficient absorbing systems consisting of long, 
slender main roots thickly beset with well developed laterals, giving rise to 
very extensive absorbing surfaces. 
7. The superior root growth resulting from aeration of the cultures with 
continuously renewed solutions was particularly reflected in accelerated top 
growth during the later stages of development. 
8. The average total yields obtained from the sand cultures were 
throughout uniformly much higher than were those obtained from the 
solution cultures. 
Laboratory of Plant Physiology, 
New Jersey Agricultural Experiment Station 
REFERENCES 
1. Allison, R. V. 1921. The relation of aeration to the development of the soybean plant 
in artificial culture. N. J. Agr. Exp. Sta. Ann. Rep. 1921: 338-345. 
2. Free, E. E. 1917. The effects of aeration upon the growth of buckwheat in solution 
cultures. Johns Hopkins Univ. Circ., n. ser. 3: 198-199. 
3. Lund, E. J. 1921. A micro-winkler method for the determination of dissolved oxygen. 
Proc. Soc. Exp. Biol. Med. 19: 63-64. 
4. McCall, A. G. 1918. Abnormal stem growth of soybeans in sand cultures with Shive’s 
three salt solution. Soil Sci. 6: 479-485. 
5. Pember, F. R. 1917. Studies by means of both pot and solution cultures of the phos¬ 
phorus and potassium requirements of the barley plant during its different periods 
of growth. R. I. Agr. Exp. Sta. Bull. 169. 
6. Shive, J. W. 1915. A study of physiological balance in nutrient media. Physiol. 
Res. 1: 327 - 397 - 
7. -. 1918. Toxicity of monobasic phosphates towards soybeans grown in soil-and 
solution-cultures. Soil Sci. 5: 87-122. 
8. Trelease, S. F., and Livingston, B. E. 1922. Continuous renewal of nutrient solutions 
for plants in water cultures. Science, n. ser. 55: 483-486. 
EXPLANATION OF PLATE XXXIX 
Above. Drip solution cultures at the age of 14 days. Culture on the left aerated, 
culture on the right not aerated. Note the superior root development of the culture on the 
left. 
Below. Same cultures as those shown above, at the age of 37 days. Culture on left 
aerated, culture on right not aerated. Note how completely the roots fill the jar on the 
left. 
