462 
Journal of Agricultural Research 
Vol. XXV, No. 11 
Table IV .—Acidity of the tops of corn plants of Series IV, 32 to 35 days old, in good 
condition, grown in the greenhouse in sandy loam, P H 7.2 
Strain No. 
Date of de¬ 
termination 
(July, 1932). 
Titratable 
acidity 
(cc. N /20 
NaOH). 
Ph 
Specific 
gravity. 
48 s (»)*. 
26 
3-7 
5-51 
I- 0135 
485 (b) 1 . 
28 
4-3 
5*49 
I- 0153 
113. 
27 
4-3 
5-49 
1. 0138 
5°7 . 
2 5 
4. 6 
5*44 
1. 0148 
326. 
26 
4-7 
5- 
1. 0152 
315 . 
26 
4-7 
5* 49 
I. 0132 
350; v . 
27 
4. 8 
5- 55 
1. 0148 
31 ( a ),. 
28 
4.8 
5-43 
I. 0156 
31 (b)‘. 
28 
5-6 
5- 34 
I. 0167 
25 
5-o 
5* 5 1 
I. 0145 
972. 
27 
5-i 
5-5i 
I. 0163 
150 . 
25 
5-2 
5- 38 
I. 0152 
Average. 
4.7 
5-48 
I. 0149 
1 Strains 485 and 31 were uneven in growth, so the best plants of each row (a) were determined separately, 
and when compared with the rest (b) show a greater add content in the less vigorous plants. 
Table IV shows that the juice of the plants of this series had a hydrogen- 
ion concentration practically the same as that of the vigorous Series I and 
a slightly lower total acidity, while both the hydrogen-ion concentration 
and the total acidity were very much lower than in the weak spindling 
plants of Series II and III. 
As these large, rapidly growing plants seemed so much more succulent 
than the spindling, slow-growing ones of Series III, it was not surprising 
to find the specific gravity measurements of their juice very much lower 
than those of that series. This fact suggests that the low acidity of the 
former compared to the latter may be due in part ter a greater water¬ 
absorbing capacity of the rapidly growing plants, resulting in greater 
hydration of the tissues and dilution of the cell sap. It is interesting to 
note in this connection that Reed (jj) found the concentration of the 
sap of certain trees to vary inversely with the rate of growth. 
SERIES v 
The fifth planting was in an outdoor plot for comparison with the green¬ 
house plants. The soil was a fine, sandy loam, slightly acid, with a P H 
value of 6.6. The season was too far advanced for corn, the cool nights 
of September and October so inhibiting its growth that the plants were 
poor and more stunted than those of any other series. They were char¬ 
acterized by narrow leaves and by very short internodes. Many were 
leaning or fallen. 
To facilitate comparisons of the acidity determinations of these slow- 
growing plants with those of vigorous ones of the same age, the averages 
of the acidity measurements for each strain are given in Table V alongside 
the corresponding values for plants of Series IV, which had been allowed 
to grow in the greenhouse until they were 8 weeks old. 
