146 
Journal of Agricultural Research 
Vol. XXVII, No. 3 
Throughout this period the acidity of the tissues in the region of the apex 
is decidedly less than that of the lower portion of the stem (fig. 8). In 
all plantings flower buds could be seen about 30 days after germination. 
The data in the second section of the table show the changes in acidity 
which are associated with the appearance and development of the flower 
bud. In earlier stages of development acidity relations in the young, 
topmost leaves, the upper portion of the stem, and the growing point 
are much the same. The appearance of the flower bud, however, is 
marked by considerable increase in acidity in the upper portions of the 
plant and the flower bud increases progressively in acidity as growth 
proceeds (fig. 8). Additional observations on other field plantings show 
further increase in acidity till a P H value as low as 5.22 is reached in the 
fully expanded blossom. On the other hand, as the seeds develop these 
show decreasing acidity till in large well-filled seeds the P H value rises to 
approximately 7.05. 
Pu SA4METEPI Of ALOWER BBSS //V //VC//E3 
rZ BO AO AS £0 _ 2.3 3 jO 
6.0 
6.2 
6.4 
6.6 
6.6 
7.0 
7.2 
7.4 
29 3 /9 2 AS 2/4 
JUNE BBlf fU/O. SEPT. 
Fig. 8.—Showing the effect of the natural change in length of day of summer and early fall on the active 
acidity of the top and base of the axis in sunflower and the change in acidity during the development 
of the flower bud (Table XII). Sunflower resembles the typical long-day plants in that within the 
seasonal range in length of day (at Washington) the active acidity at the top of the stem is less than 
that of the base. The flower bud increases sharply and regularly as growth proceeds. 
s 
> 
V ............. 
\ 
\ 
\l 
A 
—— — 
r 
70PP/VP S^SEOf 
(STEMS. fROM SUCCESS/T£ 
RL4/VT/A/GS. /3-/7/MYS 
PIETER GERM/MT/O/V.- 
—— TOP Of STEM 
< 
KT 
- - - BASE Of STEM 
SCAS: 
5 
. Of GROWTH. 
1 1 M iV 
r 
ini 1111111111 
1 1 L 1 -L 11 I.J- 
■ 1 JI 
J-lill 
iu,i i mi 
JLLI 1 LLU- 
nit 
1111 
11 . 1.11 Jl 
Lll 
Table XII .—Showing the Ph 'value of the cell sap of Helianthus annuus planted at 
intervals of two weeks during the summer and at different stages of development 
Date of 
germination. 
June 29. 
July 5.. 
July 19. 
Aug. 2.. 
Aug. 18. 
Sept. 2. 
Sept. 14 
Aug. 18. 
Do. 
Do. 
Do. 
Do. 
Aug. 2.. 
Do. 
Do. 
Do. 
Date of 
sample. 
July 12. 
July 22. 
Aug. 3. 
Aug. 19. 
Sept. 2. 
Sept. 17. 
Sept. 29. 
Sept. 2. 
Sept. 9. 
Sept. 13. 
Sept, is. 
Sept. 23. 
Sept. 9. 
Sept. 13. 
Sept. 14. 
Sept. 30. 
Number 
of days 
after ger¬ 
mination 
when 
sampled. 
Hour of 
sampling. 
11.30 a. m. 
11.35 a. ui- 
12.30 p. m. 
1.30 p. m.. 
1 p. m 
12.35 P- xn. 
9.50 a. m. . 
1 p. m. 
9.50 a. m. . 
2.50 p. m.. 
,20 a. m.- 
.50 a. m. 
9.50 a. m. . 
9.50 a. m.. 
1.15 p. m.. 
.50 a. m.. 
.30 p. m.. 
2.30 p. m.. 
( 9 ' : 
\u-! 
9 -f 
l.l 
ft 
Ph value of sap. 
Top¬ 
most 
leaves. 
Top 
of 
stem. 
7-33 
7-32 
7-33 
7.06 
7.11 
7-15 
7-32 
7.11 
Base 
of 
stem. 
6-37 
6. 39 
6. 50 
6.49 
6.12 
6.31 
5-99 
6.12 
17 
6.15 
6.83 
6.13 
Apical 
bud. 
7.11 
7.18 
7.11 
Flower 
bud. 
Diam¬ 
eter of 
flower 
bud. 
inches. 
6.89 
'A 
6.81 
X 
6. 52 
lA 
6.36 
2 
6.17 
2X 
