sept 15,1923 Acidity of Corn and its Relation to Vegetative Vigor 
459 
sion, duplicate determinations, but with their sequence reversed, were 
made on the same strains each afternoon. The results are given in 
Table I. 
Table I .—Acidity of the tops of corn plants of Series /, 36 to 39 days old, 1 in good 
condition , grown in the greenhouse in neutral sandy loam 
Strain No. 
Date of de¬ 
termination 
(May, X 9 aa). 
Morning cuttings. 
Afternoon cuttings. 
Titratable 
acidity (cc. 
N/20 NaOH). 
Ph 
Titratable 
acidity (cc. 
V/^oNaOH). 
Ph 
972 .. 
27 
4-5 
5-68 
4.4 
S- 68 
129. 
25 
4.9 
5-54 
5-0 
5-61 
507 . 
27 
4. 8 
5.60 
5-5 
S-S8 
350 .. 
2 4 
5 *o 
s-ss 
5-6 
5-56 
485 . 
24 
3-0 
5- 59 
6 . 0 
5-46 
150 . 
27 
5-6 
5-5* 
5*7 
5-55 
315 . 
26 
5-8 
5-48 
5-7 
S-44 
XI 3 . '•••••■ . 
25 
6 . 1 
5-4* 
5 * 6 
5-45 
3i . 
25 
5-8 
5- 56 
6.6 
5-S° 
326. 
26 
2 <7-4) 
a (s- 38) 
6.6 
5-44 
Average. 
i 
5-3 
5* 55 
5-7 
5 ' S3 
1 Throughout this paper age is reckoned from the date of planting. 
* Poorest plants in the plot, described as “stunted, leaf tips dead,” not included in the averages. 
The close agreement in the values obtained from morning and after¬ 
noon cuttings brings out the interesting fact that neither the hydrogen- 
ion concentration nor the titratable acidity changed measurably between 
8 a. m. and 12.30 p. m. In those cases where the measurements were not 
the same, as many show a decrease as show an increase. Evidently the 
diurnal change in acidity, reported in many plants, is not marked in corn 
grown under these conditions. 
SERIES 11 
The second set of plants was grown in another greenhouse in a sandy 
clay loam with a slightly acid reaction (P H 6.5), and only 3 or 4 inches 
deep on the bench. This series, like the preceding one, reached an aver-' 
age height of 50 cm. by the sixth week, at which time the plants were cut. 
However, the stalks were spindling and the leaves narrow, whereas the 
plants of the first set had stout stalks and the broad leaves of normal 
plants of that age. As the plants were cut, they were weighed for com¬ 
parison with those of subsequent series and found to average 44 gm. 
Green weight expresses more accurately than does height the rate of 
growth and health of the plant (7). 
Either one or two plants, depending on their size, were taken for each 
sample and the stalks and leaves expressed together. Unfortunately, 
there was not sufficient material to make duplicate measurements on 
strains 326 and 113, and the plants of No. 485 and 350 were lost. The 
acidity determinations for this group of plants are recorded in Table II. 
60096—23 - 3 
