558 
Journal of Agricultural Research 
Vol. XXI, No. 8 
When only nitrogen, phosphorus, and potassium are varied, there are 
nine possible combinations of two solutions lacking one element with one 
solution lacking two elements. The effects of two of these combinations 
on the growth of com and the assimilation of nutrients are shown in 
Tables X and XI. 
In the relative growths made by plants 33 to 48 and 49 to 64 there 
is further evidence that nitrogen is the element most needed by com 
at this stage of growth. Plants 49 to 64 made the greater growth, 
doubtless because two-thirds of their roots were supplied with nitrogen, 
while only one-third of the roots of plants 33 to 48 were so supplied. 
The relative growths of roots in the A, B, and C flasks present no 
unusual features; they are evidently dependent on the relative needs of 
the plant for nitrogen, phosphorus, and potassium, and 011 the pro¬ 
portions of the roots which were supplied with these three elements. 
Experiment VII.— The roots divided among three solutions, one of 
which lacked one element and two of which lacked two elements. 
Of the solutions named above, six combinations afford a complete 
nutrient solution; only two of the combinations, however, were tested. 
The results are shown in Tables XII and XIII. 
Plants 49 to 64 contained more nitrogen and phosphorus than plants 
33 to 48, since they had an advantage in assimilating these elements 
from the same solution. 
Experiment VIII.—The roots divided among three solutions, each 
of which lacked two elements. 
In this experiment the nitrogen was in one flask, the phosphorus in 
another, and the potassium in a third. The results are given in Tables 
XIV and XV. 
The depressions in growth and assimilation and the increase in the root 
to top ratio were greater in this experiment than in any of the preceding 
ones. 
The distribution of nitrogen and potassium between the roots and tops 
in this experiment may be of some significance; it seems to support the 
explanation offered later of the manner in which assimilation is de¬ 
pressed by a division of the roots between incomplete solutions. I11 the 
case of plants 33 to 48, the roots which were in the solution containing 
nitrogen have a higher percentage of nitrogen than the stalks and leaves; 
also, the roots from the potassium solution are richer in potassium than 
the tops. The control plants (1 to 16), however, have far higher per¬ 
centages of nitrogen and potassium in the stalks and leaves than in the 
roots. In all the preceding experiments (except plants 49 to 64, experi¬ 
ment VII), where assimilation was depressed to a less extent than in this 
experiment, the stalks and leaves are richer in nitrogen and potassium 
than the roots. 
