sept is, 19*3 Acidity of Corn and its Relation to Vegetative Vigor 467 
In general, there is no parallelism between the magnitude of the indi¬ 
vidual readings of acidity and specific gravity in the tables. However, 
certain striking instances of high sap density accompanying high acid 
content strongly suggest some interdependence. Some examples of this 
relation are the wilted plants of strain 485 in Series V (Table IV). 
These external symptoms of a water deficit were accompanied by an 
unexpectedly high acidity and high specific gravity of the juices. The 
plants of strain 972 (Series IV) were so wilted, as the result of not having 
been watered the day before, that the leaves were limp and somewhat 
rolled. The titratable acidity measurements of both leaf juice and stalk 
juice were higher than the corresponding values for the unwilted plants 
of the same strain, and their specific gravity values were abnormally 
high, 1.0317 for leaf juice and 1.0246 for stalk juice. Further indication 
of a possible relationship of these characters is found in the fact that leaf 
juices always had a definitely higher sap density than the less acid stalk 
of the same plant. However, there are so many instances of juices which 
differ widely in acidity yet show no significant difference in specific 
gravity that difference in the hydration of the tissues obviously is not 
the only factor determining the magnitude of the difference in acidity 
values. 
No conclusions can be drawn from these experiments as to the existence 
of varietal differences in acidity because the individual plants of each 
strain varied greatly in growth and vigor, and consequently in acidity, 
even when growing side by side in the same series. The varieties showing 
the most pronounced vigor, such as 507 and 485, usually were among the 
least acid in each series, suggesting that growth reactions to the environ¬ 
ment rather than inherent acidity characters were responsible for the acid 
differences. Moreover, the varieties did not keep the same relative posi¬ 
tions as to vigor in the different series, some reacting more poorly in one 
environment, while being among the best in another, thus recalling the 
work of Mooers ( 12 ) who found great differences in the relative yields of 
varieties on different soils. It would seem, therefore, that environmental 
factors, together with the capacity of the strain to respond to them as 
indicated by its vigor of growth, are more potent in determining cell-sap 
acidity then preexisting varietal acid tendencies. 
SUMMARY 
(1) The hydrogen-ion concentration of the tops of com plants ranged 
from P H 5.0 to 5.6 in the five plantings constituting these experiments, 
and was inversely correlated with the degree of vegetative vigor induced 
by the environmental conditions affecting the different plots. 
(2) The titratable acidity of these tops varied correspondingly, the 
values ranging from an average of 10 cc. of N/20 sodium hydroxid 
solution, required to neutralize 10 cc. of juice from plants of the most 
stunted plot, to 5 cc. (average) required to neutralize the same quantity 
of juice from the most rapidly growing plants. 
(3) A lack of exact correlation between the magnitude of the acidity 
measurements and the specific gravity determinations of these juices 
shows that, in general, variations in sap density were not responsible for 
the variations in acid concentration. However, a number of striking 
instances of exceptionally high acidity values accompanied by cor¬ 
respondingly high density figures indicate that the water content of the 
tissues had, at times, a measurable effect on the acid concentration. 
