440 
Journal of Agricultural Research 
Vol. XXXI, No. 6 
Table VI .—Interior temperatures of a large seedling male palm compared with 
air and soil temperatures , May 5 to May 11, 1928 
Time 
Air 
(by 
thermo¬ 
graph) 
Soil at 
2 feet 
Soil at 
3 feet 
Interior 
of 
trunk 
(at 4 
feet 
height) 
Time 
Air 
(by 
thermo¬ 
graph) 
Soil at 
2 feet 
Soil at 
3 feet 
f 
Interior 
of 
1 trunk 
(at 4 
1 feet 
height) 
May 5: 
° F. 
°F. 
0 F. 
°F. 
May 9—Contd. 
°F. 
°F. 
°F. 
0 F 
8.30 a. m_ 
89 
72. 75 
73.00 
10.45 a. m_ 
73. 75 
71.55 
73.75 
10.00 a. m_ » 
90 
73.00 
72.00 
12.00 a. m_ 
108 
73. 75 
71.55 
73.50 
12.00 a. m 
73.00 
71. 75 
1.30 p. m 
73. 75 
71.55 
73.25 
2.00 p. m_ 
*102 
73.00 
71. 75 
3.00 p. m_ __ 
73.75 
71. 55 
73.50 
4.00 p. m___ 
73.00 
b 71.50 
4.00 p. m__. 
73.75 
71. 55 
73.25 
May 7: 
5.00 p. m___ 
105 
73. 75 
71.55 
73.50 
8.15 a. m_ 
85 
74.00 
74.50 
May 10: 
11.00 a. m_ 
74.00 
73.00 
8.30 a. m_ 
87 
74.00 
72.00 
75.75 
1.30 p. m_ 
74.50 
72.00 
b 72.50 
10.00 a; m_ 
74.00 
71.55 
74.00 
3.00 p. m_ 
110 
74.00 
71.10 
72.50 
11.00 a. m —. 
74.25 
71. 55 
73.75 
4.45 p. m_ 
74. 25 
71.10 
72.50 
12.00 a. m.— 
100 
74.25 
71.55 
73. 75 
May 8: 
1.30 p. m _ 
74.25 
71. 55 
73.50 
8.00 a. m_ 
90 
75.00 
71.10 
75.00 
3.30 p. m_ 
103 
74.25 
71. 55 
73.50 
10.00 a. m_ 
74. 75 
71.10 
73.00 
5.00 p. m_ 
74.00 
71. 55 
73. 50 
11.00 a. m_ 
75.00 
71.10 
72.75 
May 11: 
1.30 p. m_ 
109 
75.00 
71.10 
72.75 
9.00 a. m_ 
80 
74.50 
72.00 
75.50 
2.30 p. m_ 
75.00 
71.10 
72.50 
10.30 a. m_ 
_____ 
74.50 
72.00 
74.25 
4.00 p. m_ 
. .. 
75.00 
70.65 
72.75 
11.30 a. m_... 
95 
74.50 
72.00 
74.00 
May 9: 
1.45 p. m_ 
102 
74.50 
72.00 
73. 75 
8.15 a. m_ 
86 
74.50 
72.00 
75.50 
3.15 p. m___ 
________ 
74.75 
72.00 
73.50 
9.45 a. m_ 
74.00 
72.00 
74.00 
4.30 p. m._. 
95 
74.50 
72.00 
74.00 
* Figures in bold-face type indicate lowest temperature for the day. 
<* Figures in italic indicate highest temperature for the day. 
THE INVERTED TEMPERATURE CURVE 
Tables I to VI and the graphs shown in Figures 5 and 6 indicate a 
fairly uniform and very significant 24-hour curve of the interior tree 
temperature. In February and early March a daily maximum was 
reached at about 9 to 10 or 11 a. m., but as the air temperature means 
advanced during the latter part of March, this interior maximum 
occurred about 6.30 a. m., and was maintained but a short time, 
followed by more or less gradual drop of from 2° or 3° to 5°, or at 
most 7°, reaching a minimum at from 3 to 5 p. m. From this a rise 
followed, unless the air temperature had dropped during the day, 
* persisting as late in the night as the readings were taken, which was 
usually not later than 10:30 p. m., although one record was kept to 
12.30 a. m., and one all night. A continuation of this rise was 
generally traced at 4.30 to 6.30 a. m., making the night temperature 
curve a part of the approach to the morning maximum. 
Whatever the factors may be, tending toward an equalization of 
the temperature of the growing tissues, the result is an inversion of 
the temperatures, holding the tissues at their highest point during 
the coolest morning hours, and at their lowest temperature during 
the maximum of the day's heat. 
NARROW RANGE OF INTERIOR TEMPERATURES 
Another matter of interest to be noted in Tables I to VI and in 
the graphs Figures 5 and 6, is the very narrow daily range exhibited 
by the interior temperatures as compared with the temperature of 
the air. During February and the early part of March the 24-hour 
range shown by the upper thermometer inserted into the growing 
region of the date trunk was only from 1.8° to 5.4°, and that of the 
