Carhon Dioxide in Maturation, etc., of Seeds. 413 



Table III. — The Effect of Increased Partial Pressures of C0 2 on Bean 

 (Vicia faba), Cabbage {Brassica oleracea), and Onion (Allium cepa) Seeds 

 in Inhibiting Germination, and the Besumption of Normal Activity on 

 the Eemoval of these Increased Partial Pressures. 







Time during 



Resulting 

 germination in 

 artificial atmo- 



Final percentages 



OUcLlcS sji. 



S66cl used 



Percentage of 

 COo in air in 



ivhu'li spprl<a tppvp 



V> 1 1JLL.11 OCCLtB n CI C 



>l 111L/11 DCCLlO 



remain in artifi- 

 cial atmosphere 



subsequently in 

 normal air. 









set to germinate. 



containing raised 

 percentage of 



raised percentage 

 of CO,. 



Of ger- 



Of good 







C0 2 . 



minations. 



plants. 







days 









Cabbage 



25 



10 



All inhibited 



72 



72 



(50 seeds) 



38 



10 



)j 



88 



88 



44 



10 



Normal germina- 



76 



76 













84 



84 





(air with KOH) 





tion at once 







Beans 



45 



8 



All inhibited 



95 



85 



(30 seeds) 



53 



8 



>, 



75 



55 





89 



8 



>> 



85 



50 













Normal germina- 



95 



85 





(air with KOH) 





tion at once 







Onion 



23 



11 



28 per cent, ger- 



44 



44 



(50 seeds) 







minated 









30 



11 



All inhibited 



50 



50 





68-7 



11 



Normal germina- 



46 



46 













60 



60 





(air with KOH) 





tion at once 







Average temperature, 17 '5° C. 



(b) The Peculiar Case of White Mustard (Brassica alba). — Brassica alba 

 was peculiar among the seeds experimented on, in that inhibition was 

 continued indefinitely after the removal of the seeds from increased partial 

 pressures of C0 2 to normal air, and was then only terminated by the treat- 

 ments described in Tables IV and V. 



White mustard seeds that have been inhibited by the action of C0 2 while 

 germinating will lie indefinitely in germinating conditions without sprouting 

 or with sporadic sprouting over long intervals. They have all the appear- 

 ance of continued vitality, and they do not become attacked by moulds. The 

 part played by the testa in securing the continuance of the inhibitory effect 

 of carbon dioxide after the removal of the inhibitory agent is of great interest. 



In the following table it will be seen that dormancy produced by CO2 

 was continued for two to three months after removal of the seeds to air, 

 suitable conditions for germination being maintained throughout. Finally 

 the seeds returned to normal activity and germinated 100 per cent, in every 

 case following the treatments described. 



