590 The Philippine Journal of Science 1920 
injury occurred, although it did occur in series I with this set - 
of salt proportions for a total concentration corresponding to 
1.60 atmospheres. It is clear that magnesium injury does not 
increase with total concentration with this set of salt propor- 
tions. The fourth set of salt proportions tested in this series 
(R5C24 on the Shive diagram, which resembled very closely 
Shive’s best solution) showed no magnesium injury in any 
of these concentrations, except a slight indication with a con- 
centration value of 5.50 atmospheres, although Shive’s best 
solution regularly produces this form of injury. It is to be 
noted that while this set of salt proportions differed from that 
of Shive’s best solution to only a small degree, yet this dif- 
ference was in such a direction as to justify an expectation of 
less magnesium injury than occurred in the Shive solution. It 
appears that solution R5C24 lies on the border line where more 
or less marked magnesium injury may or may not occur, accord- 
ing to conditions so far uncontrolled, such as those of the climate 
or the susceptibility of the individual plants. 
Dry weights.—The top yields of this series (fig. 10) bring 
out what appear to be some very important considerations. 
With the set of salt proportions (T2R4C2) giving highest yields 
in series ‘I a concentration value of 1.60 atmospheres, or per- 
haps somewhat higher, appears to be optimal for dry yield of 
tops. Both lower and higher concentrations give lower yields. 
With concentrations below this optimum, the yield falls off much 
more rapidly than with those above. It is especially interesting 
to note that a total concentration value of 0.50 atmosphere nearly 
corresponds in top yield with a total.concentration value of 4.50 
atmospheres. Lower total concentrations than the lowest here 
employed (0.50 atmosphere) would doubtless have given still 
lower dry weight values, but it is not to be expected that the 
latter would have been reduced very much in this way. It is 
noticeable, on the other hand, that the low top yield occurring 
with the highest concentration here used (7.00 atmospheres) is 
much lower than that occurring with a concentration value of . 
0.50 atmosphere. The three-salt mixture of this series (R5C24, 
on the Shive triangle) agreed very well in all particulars with 
solution T2R4C2. The graph of this set of three-salt propor- 
tiois may be regarded as indicating what would have been ob- 
tained if Shive’s set of salt proportions had actually been used. 
On the basis of this supposition, and on that of the data here 
given for solution T2R4C2, it is not to be expected that either this 
four-salt solution with chloride, or the Shive three-salt solution 
