Aug. i 4 , 1916 Agricultural Value of Impermeable Seeds 795 



It is impossible to estimate even approximately in advance the pro- 

 portion of the impermeable seeds in any given lot which will germinate 

 in any given length of time under ordinary germination conditions. 



A widely variable proportion of the impermeable seeds of alfalfa, 

 crimson clover, and the larger seeded commercial species included in this 

 investigation produce seedlings promptly in the soil under greenhouse 

 conditions or in the open field in warm weather. Only in exceptional 

 cases is this true of the impermeable seeds of the clovers, other than 

 crimson clover. 



The use of aqueous extracts from soil has no effect, and alternate 

 wetting and drying of the seeds has but little effect on the germination 

 of impermeable seeds. 



Within ordinary limits neither the depth of planting nor the firmness 

 of the soil affects the germination of impermeable clover and alfalfa 

 seeds under greenhouse conditions. These factors may affect the stand 

 secured by preventing some of the seedlings from reaching the surface. 



Storing impermeable clover and alfalfa seeds at a temperature of 50 

 C. for one day or at 45 ° for six months has little or no effect upon their 

 germinating capacity or permeability. 



In wet blotters a temperature of 36 very slightly increases the softening 

 of the impermeable seeds, but also kills some of the seeds. 



Freezing, when wet, causes the subsequent germination of many 

 impermeable seeds, but may kill some seeds which had previously 

 softened. 



Any constant temperature from i° C. to 30 has little effect upon the 

 softening of impermeable clover seeds. 



Alternations of temperature have but little effect on the softening and 

 germination of impermeable clover and alfalfa seeds if none of the tem- 

 peratures used in the alternation is cooler than 20 C. 



Alternations of temperature cause the softening and germination of 

 many impermeable clover seeds when a temperature of io° or cooler is 

 used in alternation with a temperature of 20 or warmer. The effect of 

 such an alternation of temperature is greatly increased by previously 

 exposing the seeds to germination conditions at a cool temperature 

 (io° C. or cooler), and is decreased by previously exposing the seeds to 

 germination conditions at a warm temperature (30 ). 



Even under the most favorable conditions only a small proportion of 

 impermeable red-clover, alsike-clover, white-clover, and white sweet- 

 clover seeds produces seedlings promptly in the soil when sowed in 

 warm weather. 



Impermeable seeds of red clover, alsike clover, white clover, and 

 white sweet clover will pass the winter in the soil in a freezing climate 

 without injury. At least 50 or 60 per cent of them may be expected to 

 germinate in the soil the following spring unless a part of them germinate 

 during warm weather in the winter. If this occurs, the seedlings pro- 

 duced in the winter are liable to be killed by subsequent freezing. 



