406 
Journal of Agricultural Research 
Vol. XXXI, No. 5 
Indio Thermograph Record, December 25-29, 1916 
The thermographic record at the Indio date garden for the week 
ending January 1 shows that the temperature fell to 50° F. at about 
4 p. m. December 25, and remained below 50° until 10 a. m. on the 
29th, except for brief periods on the 27th and 28th, giving a total 
as follows: 
Summation, 50° F. or below: Hours 
December 25_ 8 
December 26_ 24 
December 27_ 21 
December 28_ 23 
December 29_ 10 
Total_ 86 
The January records shown in Table II throw still stronger light 
on this question. After the entire cessation of growth December 31, 
all the varieties except the Zaheedy made a slight recovery at once 
when the maximum temperature rose above 60° F. and there were 
no frosts. There was a minimum of 28° on January 4 and a record 
of heavy frost and a minimum of 32° on January 5. With daily 
maxima of 64° it is difficult to explain a drop to zero in growth of all 
but the Asherasi on the 7th without the aid of the thermograph 
record, but an analysis of the thermograph trace for seven days 
makes the action clear (fig. 2, B). The temperature fell below 50° 
at 5.30 p. m. December 31, and until 6 a. m. January 7, when the 
zero of growth was again recorded, there were 159^ hours, of which 
for 115H hours the temperature was below 50° and 44 hours (or only 
27 per cent of the time) was above 50°. Here was a case where 
without severe minimum temperatures the long hours below 50° 
prevailed over the short hours of the day temperatures above 50°. 
Here the mean temperatures of from 46° to 51° became zero point 
temperatures, though from January 15 to 21 a mean of 44° was 
needed to accomplish the same result. 
Increasingly warm days through the 14th, with maxima ranging 
from 69° to 80° F. and minima well above the frost fine, except 
29° on the morning of the 14th, brought a return of activity so 
that daily growths of from 1 mm. to 4 or 5 and even exceptional 
cases of 6 to 9 mm. were recorded. 
The 12 days’ record from January 14 to 25, inclusive, is so sig¬ 
nificant as to deserve a close study in the table. 
The four days January 16 to 19, inclusive, with minimum tem¬ 
peratures of 33° to 44° but with their maximum of only 46° to 50° F., 
a second time gives us the clue to the zero point, for after a lag of two 
days growth entirely ceased on the Zaheedy tree (apparently having 
the highest zero point of the four) on the 18th. Deglet Noor and 
Thoory both showed slight growth gains on the 18th, 19th, and 20th, 
but came to a full stop on the 21st. The zero point in temperature 
had evidently again been reached, and the four days at 50° and 
below are as near that point as can be determined under field con¬ 
ditions. 
