LIFE SPAN OF SEEDS 57 



Table 10. Viability of Delphinium Seeds Stored under Various Conditions 



* After 7 years the temperature was changed to 5° C (41° F). 

 t After 7 years the temperature was changed to — 5° C (23° F). 



original vitality after 168 months in sealed storage at — 15° C (5° F) for 

 7 years followed by — 5° C (23° F) for the rest of the storage period, 

 although nearly all had lost their vitality in 11 months in open storage 

 at room temperature, and all the seeds were dead in 22 months under this 

 condition. Even after 193 months in sealed storage at the — 15° and — 5° C 

 (5° and 23° F) combination of temperatures, two-thirds of the seeds were 

 still alive. 



The Italian population of the United States commonly grows dandelions 

 for greens. Dandelion seeds are very short-lived in open storage. Fig. 19 

 shows the effect of temperature, moisture content, and sealed storage upon 

 retention of vitality by these seeds.^ In open storage they keep perfectly 

 for three years at — 5° C (23° F), but degenerate rapidly at room tempera- 

 ture and 5° C (41° F). In sealed storage ^\dth 7.9 per cent moisture they 

 keep perfectly at -5° C (23° F) and 5° C (41° F) and fall nearly 50 per 

 cent in vitality at room temperature for three years. The situation is 

 similar in sealed storage with 6.2 per cent water content, except that the 

 fall in vitality at room temperature is considerably less. Finally, with 

 3.9 per cent water content the seeds keep their vitality almost equally 

 well at all three temperatures, mth only a slight fall at room temperature. 

 Barton has found that repeated opening and resealing of sealed seeds 

 results in more rapid degeneration than occurs if the seeds are kept sealed 

 continuously for the whole period. She attributes this to sHght fluctua- 

 tions in water content due to opening and exposing to the air. 



Let us look at another set of storage experiments (Fig. 20) where only 

 one storage factor approached the optimum, namely, reduced and con- 

 stant moisture content \vith no reduction in oxygen pressure and labora- 

 tory temperature for storage.^ These seeds at the beginning bore from 

 8.2 to 12.5 per cent moisture, about the amount held by seeds in equi- 

 librium with the air in mid-summer at Yonkers. The seeds that were 



