776 



Journal of Agricultural Research 



Vol. VI, No. 20 



Heating in wet blotters. — Seeds which remained hard after a 6-day 

 germination test at 24 C. were subjected in the wet blotters to a tem- 

 perature of 36 ° for the following seven days, during which time duplicate 

 lots remained at 24 . Table VII shows the average percentages which ger- 

 minated, and which softened but did not germinate. 



Table VII. — Softening and germination of impermeable clover and, alfalfa seeds at 24 



and at j6° C. 



i. A larger percentage of the seeds softened at 36 than at 24 . C. 

 The differences were small with red-clover, white-clover, and sweet- 

 clover seed, somewhat larger with alsike-clover and alfalfa seed, and 

 over 16 per cent with crimson-clover seed. 



2. With the exception of white-clover seed at 36 C. nearly all the 

 seeds which softened germinated. However, a somewhat larger propor- 

 tion of the seeds which softened failed to germinate at 36 than at 24 . 



In view of the very slight effect of heating at 36 C. for seven days 

 in wet blotters, it hardly seems possible that soaking clover seeds over 

 night in water at 34 before planting can bring about the germination 

 of impermeable seeds as suggested recently by Muller (13). 



EFFECT OF FREEZING TEMPERATURES ON THE GERMINATION OF IMPERMEABLE 



LEGUMINOUS SEEDS 



One instance has already been mentioned in which impermeable sweet 

 clover seeds previously lying dormant in the soil produced seedlings 

 after a few days of freezing weather. (See Table VI.) A series of experi- 

 ments was begun late in December, 1909, to test further the effect of 

 freezing temperatures on the subsequent germination of impermeable 

 leguminous seeds. The seeds used had lain in water without softening 

 for 1)4 to 5 months previous to the beginning of the experiment. 



Different lots of the seeds were tested in a germinating chamber at 

 about 20 C, in very moist soil in drinking glasses which were covered 

 with black paper to exclude the light, and in soil in greenhouse flats. All 

 of the seeds were subjected to freezing temperatures either before or 

 during the germination tests, as follows: 



