74 THE VITALITY AND GEKM1NATION OF SEEDS. 



all being based on the vitality of the controls, as shown by the tests 

 made at that time, the standard being 88 per cent for the" cabbage mid 

 84.5 per cent for the onion. 



A discussion here hardly seems necessary, as there can be no doubt 

 that seeds retain their vitality much better in moist climates if pro- 

 tected from the action of the atmosphere. This may be accomplished 

 by dipping the packages in paraffin or b} r putting the seed in bottles. 

 Disregarding the expense, bottles surpass paraffined envelopes as a 

 means for the preservation of vitality, and also in the ease with which 

 the seed can be put up. The results are more certain if care is exer- 

 cised in selecting good corks. 



RESPIRATION OF SEEDS. 



From a practical point of view it has been conclusive^ shown that 

 moisture is the controlling factor in seed life. Seeds stored in a 

 humid atmosphere soon lose their vitality, but if carefully dried and 

 protected from moisture life is greatly prolonged. 



The question at once presents itself: In what way does the presence 

 of increased quantities of moisture cause a premature death of the 

 seed, or why is vitality prolonged if the water content of the seed be 

 reduced? 



In a measure, the answer to this question is respiration. Seeds as 

 we commonly know them absorb oxygen and give off carbon dioxid; 

 that is, respire./* During their respiratory activities the energy 

 stored within the seed is readily evolved, the vital processes are 

 destroyed, and life becomes extinct. The intensity with which respi- 

 ration takes place is largely dependent upon the humidity of the sur- 

 rounding atmosphere, which ultimately resolves itself into the amount 

 of water in the seed. The respiratory activity is directly propor- 

 tional to the quantity of moisture absorbed by the seed up to a certain 

 point, attaining its maximum during the process of germination. It 

 has been fbund that a decrease in the water content results in a cor- 

 responding\diminution in the intensity of respiration and consequently 

 in a prolongation of the life of the seed as such. 



Bonnier an<r Mangin^ were the first to show that respiration in liv- 

 ing plants increases with an increase in the humidity in the surround- 

 ing air. As this is true for growing plants, it is even more marked 

 in stored seeds. Maquenne c suggested that a reduction in moisture 

 is accompanied by a reduction in respiration, but at that time no 

 experiments had been made to show that such was actually the case. 



Kolkwitz (Ber. d. deutsch. Bot. Ges., 19: 285-287, 1901) reports respiration in 

 recently ground seeds. 



&Ann. sc. nat. bot, ser. 7, 2: 365-380, 1885. 

 'Ann. Agron., 26: 321-332, 1900. 



