352 BOTANICAL GAZETTE [APRIL 
the past decade we have received many quite novel propositions and suggestions 
from this group of workers, most of which were read with greater or less lack 
of conviction by agricultural scientists. With the advance of time, however, 
most of these new ideas have continually gained ground throughout the world. 
Aside from its general value as an example of an exceptionally rational 
study of a very complex and difficult set of natural relations, the keynote of 
the present book is perhaps suitably expressed by the following sentence taken 
from p. 17: “Just as the phlogiston theory passed away when the elementary 
nature of oxygen was established and LAvoIsIER taught the scientific world to 
use the balance, so the plant food theory of fertilizers must pass with increasing 
knowledge of the relation of soil to plant and the application of modern methods 
of research to the problem.”’ 
t is emphasized throughout that the problems here involved are dynamic; 
that the soil, as well as the plant, are the seats of continuously changing 
chemical and physical processes; thus no static interpretation of the environ- 
ment of roots is of much avail, and the general failure of soil analyses to answer 
the fundamental question with which we are concerned seems to have been 
due to the failure of such methods to bring out the dynamic nature of soil 
phenomena. A chapter is devoted to a somewhat thorough discussion of the 
concentration and the nature of the mineral solutes of the soil solution, with 
reference to-the conditions which control these features and keep them in 
constant change, always tending toward equilibrium but probably seldom 
attaining it. Then follows a discussion of soil absorption, with a clear setting 
forth of the logical fallacy of the prevalent interpretation of apparent soil 
acidity. 
In the chapter on “The balance between supply and removal of mineral 
plant nutrients,” McGer’s startling series of terms (‘“‘run-off,” “cut-off,” 
“fly-off’’) to denote the superficial and subterranean drainage and the loss by 
evaporation, respectively, from the soil has been adopted. The reviewer can 
see so little tendency of modern serious English to revert to this fundamentally 
Teutonic style of etymology that he cannot but look askance at these last two 
newly coined expressions. This chapter is the weakest in the book, and most 
readers will feel that the question “Is the movement of mineral plant nutri- 
ments toward the surface soil equal to or in excess of the removal by drainage 
waters and garnered crops?” (p. 75) is not answered with data or considera- 
tions which even “‘appear sufficient for the present purpose.’ The approxi- 
mations given of the number of tons of potassium, etc., annually carried, in 
the United States, toward the soil surface, removed by crops, and washed into 
the sea are of no interest as regards any particular plant or soil. The question 
must be settled with reference to particular soil areas, by experimental studies 
yet to be accomplished. However, the author is quite aware of the weakness 
of these calculations, and admits that “‘it is wise to avoid giving them too much 
emphasis.” His thesis against the Lresic theory of fertilizer action gets its 
support from quite different lines of argument. 
