24 



THE VITALITY AND GEKMINATION OB' SEEDS. 



From the foregoing table it will be seen that precipitation is a factor 

 of much greater importance than temperature. In order to show the 

 real value which the amount of precipitation furnishes as a basis for 

 judging the length of time that seeds will retain their vitality when 

 stored in localities having a marked difference in the amount of rain- 

 fall, the results set forth in the above table are represented diagram- 

 matically as follows: 



Effect of precipitation on vitality. 



A discrepancy is very marked for Durham, N. H., which may be 

 partially explained by considering again the conditions under which 

 the seeds were stored. It will be remembered that these samples of 

 seeds were stored in a hall which opened directly into a chemical labora- 

 tory. It is quite probable that the low percentages of germination 

 were due to the injurious action of gases emanating from the labora- 

 tory. Of these gases, ammonia probably played a very important part, 

 as it is well known that seeds are very readily injured when subjected 

 to the action of ammonia. 



It is to be understood that the above comparisons are somewhat 

 indefinite. If the amount of rainfall were equally distributed through- 

 out the year a definite ratio could, in all probability, be established; 

 but in the majority of places there are alternating wet and dry seasons, 

 which make such a comparison very difficult and unsatisfactory. Yet 

 for ordinary considerations it is sufficient to say that seeds will retain 

 their vitalit} T much better in places having a small amount of rainfall. 

 For more exact comparison other factors must be taken into account, 

 especially the relative humidity, mean temperature, and temperature 

 of the dew-point, which ultimately resolves itself into the absolute 

 amount of moisture present in the atmosphere. 



EFFECT OF MOISTURE AND TEMPERATURE UPON VITALITY. 



From the foregoing experiments it is quite evident that moisture 

 plays an important part in bringing about the premature death of 

 seeds and that the detrimental action of moisture is more marked as 



