1920] 
DUGGAR—INSOLUBLE SALTS IN BALANCED SOLUTIONS 311 
and these facts are brought out in the special explanations 
given in connection with the particular tables. 
In table 1 there are given in the second and third columns 
(under “concentration,” 1 and 11) the quantities of the salts 
used, these being expressed in grams of the pure salt or in cc. 
of a standard stock solution. The concentration numbers occur 
again in the fifth column, indicating to which concentration 
the data in the remaining columns refer. When given in grams, 
the quantities indicated were used in 240 cc. of water, and no 
change of these constituents was made throughout the interval 
of growth. 
The quantities given in cc. also require explanation. KNO.;: 
the stock solution employed for every culture in which this 
salt occurs except No. 15 contains 35 grams KNO, in 1000 cc. 
of water, and the use of 10 cc. per culture of 240 cc. gives a 
concentration of this salt in the culture solution approximately 
three times as great as in solution B (No. 15 in this table). It 
is approximately two-thirds as strong as the concentration of 
KNO, in one of the “best” cultures of Livingston and Totting- 
ham (718), that is, R.C., referred to in my earlier paper (Duggar, 
'20) as solution C. Moreover, in the two cultures (No. 12 and 
No. 14) in which Mg(NO;), or NaNO; was substituted for KNO,, 
the strength of the solution was such as to afford a quantity 
of NO, equivalent to that of the KNO, in all cultures except 
No. 15. MgSO.: the stock solution, 12 grams in 1000 ce. of 
water, is the same as that used in solution B (No. 15 of this 
series). The concentration of soluble ferric phosphate is like- 
wise made the same as in solution B (No. 15 of this table). The 
control solution in this series is solution B, No. 15 of the table, 
previously described in detail, as noted above. Additions of 
10 cc. of KNO, were made to each culture (240 cc.) containing 
this salt at intervals of 7 days, and at the same time the solu- 
tion in No. 15 (solution B, control) was renewed. 
A glance at table r, and more especially a study of fig. 1 (wheat), 
indicates that the differences between the two “concentrations” 
or strengths of solutions are within the probable limits of varia- 
tion commonly found in duplicate cultures. 'The average of 
the two similar control cultures in solution B (No. 15) is ex- 
ceeded by No. 2. The latter culture differs from the control 
