Sept. 1, 1925 
Minimum Temperature for Growth of Date Paim 
405 
30th must be credited to the lower maxima. As the minima of this 
period were from 28° to 39° F., a little higher than those of the re¬ 
covery period from December 13 to 18, the way is fully cleared for a 
zero point determination. The sharp check in growth was recorded 
on the morning of the 27th following the maximum of 48° at 2 p. m. 
on the 26th. A little recovery was made on the 28th, but the record 
of the night following shows a check in growth to a fraction of a milli¬ 
meter on all trees, and all but the Deglet Noor tree show practically 
zero point of growth on the 30th. It is evident that the conditions 
of the observations do not enable one to decide positively whether 
it required all of the 48° to inhibit growth, or whether 50 or 51 
, 6 JIT 6 M 6 Iff 6 M 6 Xff 6 M 6 Iff 6 M 6 UL 6 M 6 Iff € M 6 M 6 M 6 _ 
«» , j- i i i ^ i i i jr -i- i rjBq rrwzi 7 / jjj i / i / 
would have accomplished this result. This period must be given its 
weight with the other records. , e 
The period of exposure of the plants to a temperature of 50 r. 
or below was longer than is apparent from the tables. Keterence 
should here be made to the transcript from the thermograph sheet 
for December 25 to 30 (fig. 2, A) which, while varying a httle from the 
records of the standard maximum and minimum theimometers, 
affords on an occasion like this a most illuminating exhibit ol the 
temperatures to which the plants were actually exposed. Assuming 
the minimum temperature for growth to be 50 , The graph shows for 
how long a period the temperature was below the 50 line and how 
little value the very short period of 2 or 3 degrees above 50 in the 
middle of the day could have had. 
