[Vor. 7 
24 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
The C group of cultures (Livingston-Tottingham medium) is 
here introduced for the first time. Explanations already given 
explain the culture indices in this group, except in the following 
cases: CxNH, CxGC, and CxGP. In the first mentioned one- 
half the atomic proportion of nitrogen is supplied as (NH4),SO,, 
and in the last two calcium glycero-phosphate is added to re- 
place monobasie caleium phosphate. In CxGC the atomie 
proportion of Ca is kept the same as in CxO, while in CxGP it 
is the phosphorus which is equivalent. 
Under the conditions of these experiments the Aw cultures, 
particularly, were less satisfaetory than usual, possibly in large 
part due to the high temperature prevailing towards the end of 
the period. The series was discontinued earlier than planned 
owing to the drying of the leaf tips of wheat and even of some 
entire plants. On the whole the wheat cultures show many 
inconsistencies, but despite this also some strikingly interesting 
results. 
Increasing the Px exponent by means of the dibasic phosphate 
may under these extreme conditions more than treble or quad- 
ruple the growth quantities. It is probably a matter of shifting 
the sum of conditions from the side of toxicity to that of growth 
maintenance. Even in the case of the C solution, increasing the 
Pu exponent is here a factor in promoting growth increase. 
Under other conditions I have not found this to be true, as will 
be indicated later. . 
The addition of aluminium hydroxide is under these condi- 
tions distinctly favorable, as seen by comparing the following 
pairs, AwO and AwAl (also AwO and Awh/Al), BwO and 
BwAl, CwO and CwAl. The value of this reagent is doubtless 
in part due to its action as a buffer. 
The temperature was most favorable for the corn cultures, 
and they exhibited, on the whole, an unusually vigorous growth. 
The green weight determinations are an accurate indication of 
growth extent but not of appearance. The B group was dark 
green in color, with heavy purplish stems; while both the A and 
C groups were strongly chlorotic. Chlorosis was much intensi- 
fied during the last week of growth, and it seemed probable 
that if these cultures were longer maintained, a considerable 
reduction in the growth rate would occur. It is assumed, how- 
