Aug. i 4 , 1916 Agricultural Value of Impermeable Seeds 



791 



Table XIV. — Production of seedlings by impermeable seeds; assembled results of 



different experiments 



° When alfalfa seeds were in a frozen medium during any part of the experiment, nearly all seedlings 

 were produced before freezing occurred. 

 b In 2 months. 



c Calculated from heads embedded in the soil. 

 d Calculated. 



i. In each series of tests a large proportion of the impermeable alfalfa 

 seeds produced seedlings in the soil. It should be remarked that in each 

 series of tests nearly all of the seedlings produced from impermeable 

 alfalfa seeds appeared during the first month or two of the experiment 

 and that very few alfalfa seedlings appeared after the freezing of the soil 

 except when the seeds were too cold to germinate from the beginning of 

 the test period until after the freezing had occurred. (See Table VIII 

 and accompanying text.) An examination of alfalfa seeds which had 

 passed one winter under the parent plants shows that continued severe 

 freezing and thawing in wet soil will soften and kill practically all (p. 783). 



2. With each of the various kinds of clover the percentage of seedling 

 production was small when no freezing of the soil occurred during the 

 experiment. 1 Seedling production from impermeable clover seeds was 

 greatly increased by the freezing of the soil and was greatest (except with 

 sweet clover) in the series of field tests which were continued for a year. 



In every series of experiments in which check tests were made in the 

 germination chamber the average percentage of seedling production both 

 of alfalfa and of the clovers was greater than the average percentage of 



1 In a few cases with individual lots of seed of alsike clover and white clover, a large percentage of the im- 

 permeable seeds produced seedlings in a short time in soil in a moderately warm greenhouse. These cases 

 were so rare as to be almost negligible. 



