1920] 
DUGGAR—H-ION CONCENTRATION AND NUTRIENT SOLUTIONS 45 
also require consideration. An analysis of the differences 
between the Shive and the Livingston-Tottingham solution 
shows that the latter contains a relatively greater concentration 
of K and NO; ions and a lower concentration of Ca, Mg, PO,, 
and SO, Serious typographical errors in one of their tables 
(table three, page 345) have led Livingston and Tottingham ('18) 
into error in the statement that in the R;C, solution there are 
2.89 times as many atoms of Ca as of K per unit volume. Asa 
matter of fact the partial volume atomic concentration of the 
RC, solution of Livingston and Tottingham contains more than 
10 times as much K as Ca, while R,C, contains more than 8 times 
as much K as Ca, and nearly 6 times as much Mg as Ca. The 
Mg : Ca ratio of R¿C, is very nearly 2:1. In both of the best 
Livingston-Tottingham solutions the ionie concentrations of 
K and NO; are greatest. It seems quite probable that this 
factor, together with the variability in H-ion concentration of 
KH;PO,, is accountable for the better growth in these solutions. 
SUMMARY AND TENTATIVE CONCLUSIONS 
The experiments reported in this paper were undertaken 
primarily to determine the influence of variations in hydrogen 
ion concentration on the yield of certain seed plants in solution 
cultures. As the work progressed, however, many modifications 
were suggested, and some of these involved in no way a con- 
sideration of hydrogen ion concentration at points which might 
be regarded as critical for the growth of the crops used. 
The selection of several culture solutions seemed necessary in 
order that some diversity might be introduced in the salt pro- 
portion or composition factors. The solutions employed, and 
their designations, were as follows: solution A, a slight modifica- 
tion of one of Shive's “best” solutions; solution C, a slight 
modification of one of the best Livingston-Tottingham combina- 
tions; and solution B, based in part upon the Crone combina- 
tion of salts, but with this essential difference, namely, that 
“soluble ferrie phosphate" was used in place of the “insoluble” 
iron salt. Each of the solutions first mentioned contains a 
monobasie phosphate, and with theoretically pure chemicals 
should yield culture solutions with a Py exponent about 4.5. 
Solution B may vary, in my experience, from a hydrogen ion 
