464 
Journal of Agricultural Research 
Vol. XXV, No. xx 
smaller in the rapidly-growing plants of Series IV, was 1 to 2 or greater 
in the slow-growing plants of Series V. 
To illustrate these differing characteristics of the plants of Series IV 
and V and also the extreme variations which are found in the acidity of 
plants of the same strain, some titration curves obtained with plants of 
No. 326 are given in figure 1. The data for stalk and leaves of a plant 
of less than average acidity from Series IV are plotted alongside those of 
a plant of more than average acidity from Series V. 
The slope of the curve representing the stalks of the vigorous plants 
is steeper than that of the slow-growing ones and shows that the titratable 
acidity of the latter is more than three times that of the former. The 
curves representing the leaf acidities show a similar relation. The curve 
for the stalk juice of the poor plant starts below but crosses that of the 
Fig. z.—E lectrometric titration curves of leaf and stalk juices of Reid Yellow Dent corn from vigorous 
plants (Series IV) from tbe greenhouse and stunted plants (Series V) from the field. 
leaves, a relation shown by the curves for the leaves and stalk of every 
plant in Series V, but for none of the plants of the vigorous series. 
The acidity data for strain No. 150 are not included in Table V because, 
in both Series IV and V, these plants appeared diseased and not compar¬ 
able with the others. The leaves were crinkled, spotted, and dead at the 
tips, with the lower leaves prematurely dead. In Series IV, both the hy¬ 
drogen-ion and titratable-acid concentrations in these leaves were defi¬ 
nitely higher than in any others, being P H 5.26 and 12.5 cc. (NaOH), 
respective, while the corresponding values for the stalks of the same 
plants were lower than the average concentration, being P H 5.66 and 2.3 
cc. Likewise, in Series V the hydrogen-ion concentration of the leaves 
of strain 150 seemed abnormally high with respect to the corresponding 
titratable-acidity measurement, but the acidity measurements of the 
stalks were much lower than those of any other strain in the plot. More¬ 
over, in all the plants of every other strain in Series V the P H value of 
the stalk was at least 0.2 below that of the leaves; yet in these diseased 
plants of strain 150 the figures were P H 5.35 and 5.37, respectively. 
