780 



Journal of Agricultural Research 



Vol. VI, No. 20 



During the first few days of the test from 5 to 7 per cent of the seeds 

 softened under each temperature condition, showing that not all the 

 easily permeable seeds had been removed by the previous soaking. 

 After the first seven days the rate of softening varied according to the 

 temperature conditions of the different tests. 



1. When the alternation of temperatures from the ice box to 30 C. 

 was used after a period of incubation in the ice box the seed softened 

 rapidly for a few days, but the rate of softening diminished greatly 

 within a week and soon fell off almost entirely. 



SO 



Fig. 4. — Curves showing the rate of softening of impermeable red-clover seeds under different temperature 



conditions. 



2. While 32 per cent of the seeds softened when the alternation of 

 temperatures was used after 35 days in the ice box, only 22 per cent 

 softened with the same alternation after 14 days in the ice box. 



3. When the alternation of temperatures followed 35 days at 30 , 

 only 2 per cent softened in 19 days. 



Results similar to those just outlined have been obtained with red- 

 clover, alsike-clover, white-clover, and sweet-clover seeds which had pre- 

 viously remained impermeable in wet blotters for from two years to five 

 years. The alternation from i° to 30 C. has been as effective as the 

 alternation from io° to 30 . The alternation from i° or io° to 20 has 

 had somewhat less effect. In any case the effectiveness of an alternation 



