74 THE VITALITY AND GERMINATION OF SEEDS. 



all being- based on the vitality of the controls, a.s shown by the tests 

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

 84:. 5 per cent for the onion. 



A discussion here hardly seems necessar}^, as there can ])e no doubt 

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

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

 by dipping- the packages in paraffin or l)y 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 l)e put up. The resvilts are more certain if care is exer- 

 cised in selecting good corks. 



RESPIRATION OF SEEDS. 



From a practical point of view it has been conclusivel}'^ 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 greatl}^ 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 TespiTatio7i. Seeds as 

 we commonly know them absorb oxygen and give off car])on 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 activit}^ is directly propor- 

 tional to the quantity of moisture absorbed l)y the seed up to a certain 

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

 has been found 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 and 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'" 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. 



6 Ann. sc. nat. bot., ser. 7, 2: 36.5-380, 1885. 

 cAnn. Agron., 26: 321-332, 1900. 



