344 
B. E. LIVINGSTON AND W. E. TOTTINGHAM 
ion being used in a sense exactly analogous to that commonly attri- 
buted to the corresponding term gram-molecule. It will be noted 
that the partial volume-atomic concentration value for H is, in this 
same solution, twice as great as that for K, H2PO4, and PO4, which 
should be clear from the formula of the salt referred to, KH2PO4. 
The introduction of S and N at the bottom of table 3 does not refer to 
the existence of such atoms as ions in the solutions, but has reference 
only to the relative numbers of these atoms present. That these two 
elements be considered separately in a full description of a nutrient 
solution seems highly advisable; first, because they are frequently so 
considered in the literature of nutrient solutions, soil analyses, etc., 
and second, because it seems highly probable that the supply of these 
elements to the plant may frequently be important, aside from the 
particular combinations (compounds or atomic groups) in which they 
may be supplied. It may be once more emphasized that the use of 
weight percentages (parts per million, etc.) to designate the partial 
concentration characteristics of solutions and soils ought to be discon- 
tinued in this sort of study, since such terminology is not only mean- 
ingless in any thoroughgoing physiological or chemical discussion, but 
is actually misleading to many readers and clouds the very important 
issues involved. 
The fourth column of table 3 presents the respective values of the 
third column in relative form, the value given for K in the second 
column (for the solution R5C2) being here taken as unity throughout. 
These values thus represent the numbers of the respective atoms, etc., 
present in each solution, per unit of volume, in terms of the number of 
potassium atoms in solution IR5C2. It appears, for example, that 
solution IR5C2 contains 2.89 times as many calcium atoms as it does 
potassium atoms, per volume unit. The values of the last column of 
table 3 are likewise relative, but here the partial volume-atomic (or 
volume-ionic) concentration of the ion or atomic group in question, in 
solution IR5C2, is taken as unity. As an illustration, it is apparent 
that there are only half as many atoms of calcium, per unit of volume, 
in solution IIIR6C1 as there are in solution IR5C2. 
The data of table 3 make it clear how very dijfferent are the atomic 
and ionic proportions in Shive's solution IR5C2 and in our best solution, 
IIIR8C1. The latter can supply to the plant much more potassium 
and very much more of the nitrate ion than can the former; on the 
other hand, the supplies of calcium, magnesium, sulphate, and phos- 
