130 BOTANICAL GAZETTE [februar* 



the percentage of water at several temperatures at the time of loss 

 of viability. 



Seeds have a high metabolic activity at time of fall. Where 

 viability and vigor are so closely allied with high water content, 

 it is logical to suppose that the initial vigor can be retained for 

 some time by holding the water percentage at the initial content, 

 and by lowering the metabolic activity. Seeds at maturity and 

 for some time thereafter give off considerable amounts of C0 2 . 

 For a number of samples at time of fall the yield of C0 2 was esti- 

 mated as approximately 7 mg. per gram of dry weight per 24 hours 

 at 2 5 C. If we consider 7 mg. as the amount of C0 2 respired in 

 24 hours at 25 C, the seeds would soon exhaust their store of food 

 if the initial activity were maintained. The carbohydrate present 

 would be entirely exhausted and the seeds die of starvation within 

 approximately 120 days if this initial intense respiratory activity 

 were maintained. At this rate it would be impossible to hold seeds 

 just below the point of saturation at the higher temperature for 

 any great length of time. Seeds, however, can be held for some 

 time stored over water at low temperatures. Seeds harvested in 

 the spring of 191 7 were stored over water in desiccators at io° C, 

 and continued to give 95-100 per cent germination until November 

 191 7. There was, however, an abnormal development of the hypo- 

 cotyl during the latter part of the storage period at io° C. No 

 alkali was placed in the desiccators to prevent CO, accumulation, 

 so it is impossible to say just what part was played by the carbon 

 dioxide in the preservation of the seeds at this temperature. In 

 the spring of 19 18 seeds were stored over water in a large desiccator 

 at o° C. A bottle of strong alkali was also placed in the desiccator 

 to prevent accumulation of a C0 2 blanket. These seeds were 

 discarded after 102 days' storage, and at this time seeds were 

 giving 100 per cent germination. They had retained their initial 

 vigor and appeared to be normal in every respect. Perhaps many 

 other seeds of this general behavior would retain their viability 

 and vigor for considerable periods when placed in similar storage 

 conditions. Seeds can be kept for a considerable period at tempera- 

 tures just below the freezing point. After 50 days seeds stored 

 at — 5 C. gave good germination. At this low temperature care 



