Feb. 3,1923 Use of A Iternating Temperatures in Seed Germ ination 325 
weather was very warm. The temperature of the soil for the rest of 
June was only slightly warmer than in May. 
The temperature range for 24 hours at a depth of 1 inch was nearly 
always more than io° C., averaged about 16 0 , and not infrequently 
amounted to as much as 20°. The smallest range on any day was 
6° and the largest 23.5 0 . 
A/6/A7&&? 
Fig. 18.—Percentages of germination of eight lots of celery seed with four alternations of temperature. 
Seedling production in the field 
Beginning with March 26, field tests were started every two or three 
days until early in June, seed from the same lots always being used. 
In each test 500 seeds of each lot were planted, and a record was kept 
of the number of days before the appearance of the first seedlings and 
of the number of seedlings appearing at intervals of a few days thereafter. 
