Influence of A eration of Nutrient Solution. 19 7 
of the plant are expressions of our present knowledge of the life of 
the plant as a whole. 
The detachment between plant physiology and agriculture 
might be removed if a working principle in regard to the physio¬ 
logical relations of plant processes were evolved which embodied 
the activities of both sub-aerial and subterranean parts of the 
plant. This is highly desirable, but it must be admitted that it 
seems far away at present. 
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