784 



Journal of Agricultural Research 



Vol. VI, No. 20 



of the pod and a part of the time the protection of a snow cover. Of 

 seeds which were gathered from the same cultivated rows the preceding 

 fall and stored in the laboratory, 23 per cent germinated, 71 per cent 

 were impermeable, and only 6 per cent were dead. 



PRODUCTION OF SEEDLINGS BY IMPERMEABLE SEEDS DURING ONE YEAR 

 IN GREENHOUSE FLATS WITH FREEZING AND THAWING 



Seeds of a number of lots of red clover, alsike clover, white clover, 

 sweet clover, crimson clover, alfalfa, and okra were sowed in rows in 

 greenhouse flats on March 18, 191 1, and the tests were continued for 12 

 months. 



From November 18 to December 11 and again from December 20 to 

 January 25 the flats were outdoors. Each of these periods included 

 some very cold days during which the soil in the flats became thoroughly 

 frozen. 



During the eight months previous to November 18, during the nine 

 days between the two outdoor periods, and again from the end of the 

 second period out of doors, on January 25 to the end of the experiment 

 on March 19, 191 2, the flats were kept in a greenhouse. 



At the end of the first 11 days with the clovers and alfalfa and at the 

 end of the first 22 days with okra the percentages of seedling production 

 in the greenhouse flats were approximately the same as the percentages 

 of germination in a germinating chamber in, respectively, 4 and 10 days. 

 All seedlings which appeared after the first 11 or 22 days were considered 

 as being produced by impermeable seeds. 



Although the experiment was continued in the greenhouse for nearly 

 two months after the end of the second period of freezing, very few 

 seedlings were produced after the first week of that time. 



At the end of the experiment the soil was dried, broken up, and sifted 

 through sieves of the proper sizes, and as many as possible of the seeds 

 which still remained impermeable were recovered. 



Table XI. — Production of seedlings by impermeable clover, alfalfa, and okra seeds 

 when submitted to freezing and thawing 



