[VoL. 7 
4 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
indicated in the Shive solution, there is no noticeable precipita- 
tion, even on standing. There is every reason to believe that 
this substance is an excellent source of iron. The Shive solu- 
tion prepared in this way is designated solution A, and it is best 
to think of it as solution A, because, as developed later, Shive 
does not report the Px for his solutions, and this three-salt solu- 
tion may possess very different values in plant growth, depend- 
ing upon the grade or reaction of the monobasic phosphate 
employed. 
The original Crone solution is made up as follows: water, 
1000 ec.; KNO,, 1 gm.; CaSO,, .5 gm.; MgSO,, .5 gm. ; Cas(PO4)», 
.25 gm.; and Fe;(PO,): .25 gm. In our solution we have halved 
the concentration of the first two salts, omitted the tricalcium 
phosphate, and substituted for the ferrous phosphate the “sol- 
uble iron phosphate" above mentioned. In fact, the solution as 
I have used it may no longer be called the Crone solution, but it 
was of interest in this work at the time, not because it was 
expected to compare favorably with solution A above, but rather 
because it differed widely in the combinations of the components 
and had afforded in my work very good, healthy growth. The 
partial volume-moleeular proportions are as follows: KNO,, 
0.00495; CaSO,, 0.000726; MgSO,, 0.000526; and “soluble iron 
phosphate," 0.125 gm. per 1000 cc. It will be noted that this 
is in reality a four-salt solution differing also notably from the 
earlier solutions of Sachs, Knop, Pfeffer, and Meyer. Inasmuch 
as the iron salt supplies also the phosphate, this B solution 
contains a higher concentration of Fe than the usual culture 
solution. There is more or less precipitation of a light or slowly 
settling iron salt, when the combined solution is prepared. 
However, by adding the soluble ferrie phosphate last and at the 
greatest dilution possible under the conditions a light precipitate 
only is formed, and this develops slowly in the form of suspen- 
sion films. It introduces no difficulties into the preparation of 
the solution, though perhaps renders its composition somewhat 
less definite. The films are so light that it is not difficult to 
remove uniform samples from the stock flasks. The osmotic 
value of this solution has not been determined, but it is obviously 
much less than that of the Shive solution, the latter being about 
1.75 atmospheres. 
