l6o6 AORICULI'UKAI, SKEDS 



germinate promptly when the seed coat is broken or becomes permeable. 

 The viability of fresh impermeable seeds is frequently greater than that 

 of fresh seeds of the same species which are permeable. vSeeds of the 

 common clover, alfalfa and hairy vetch which are impermeable at the end 

 of three to five j^ears under laboratory conditions of storage retain their 

 vitality apparently unimpaired up to that time. The viability of the 

 permeable seeds in the same lots decreases slightly in the second and third 

 year and more in subsequent years. 



In dry storage nearly all impermeable alsike clover, white clover and 

 sweet clover seeds remain impermeable until at least 2 or 3 years old. Im- 

 permeable red clover seeds become permeable gradually in dry storage, 

 but from one third to two thirds of them may still be impermeable after four 

 years. Okra seeds become less permeable as their age increases. 



In wet blotting paper nearly all impermeable lucerne, crimson clover, 

 hairy vetch and okra seeds soften and germinate in one year, though 

 a verv^ few may remain impermeable even after three or four years. Im- 

 permeable seeds of red clover, alsike clover, white clover and sweet clo- 

 ver soften and germinate more slowly, but with no uniformity as to 

 rate. All germinate within one year in some cases, while in other cases, 

 over 50 per cent are still impermeable after four years. 



Impermeable clover seeds which were thoroughly matured before har- 

 vesting soften and germinate more slowly under conditions favourable 

 for germination than do impermeable seeds of the same species which 

 were less well matured ; they also become permeable more slowly in dry 

 storage. Impermeable seeds become permeable more rapidly in wet 

 blotter than in dry storage. 



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 lucerne, crimson 

 clover and the larger seeded connnercial species included in the investi- 

 gation 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 seed of the clovers, other than crimson clover. 



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

 wetting and drying of the seeds has but httle 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 lucerne seed 

 under greenhouse conditions. These factors may affect the stand secur- 

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



vStoring impermeable clover and lucerne seeds at a temperature of 

 122° F. for one da^^ or 113° for six months has little or no effect upon their 

 germinating capacity or permeability. 



In wet blotting paper a temperature of 107° F. very shghtly increases 

 the softening of the impermeable seeds, but it also kills some of the seed's 



