' 



140 



BOTANICAL GAZETTE 



[FEBRUARY 



cent. In the seeds stored out of doors and in desiccators over water 

 there was no indication of increased water holding capacity accom- 

 panying after-ripening. Seeds stored in desiccators at low tempera- 

 tures over water are completely after-ripened several weeks before 

 seeds stored out of doors. Table V shows how after-ripening 

 progressed in seeds stored out of doors. As after-ripening pro- 

 gressed, less and less time was required for the completion of this 

 process when placed in the germinator at io° C. 



TABLE V 



Put to germinate at io° C. 



1 



Percentage of germination after number of days indicated 





2 



3 







4 



5 







6 



8 



12 



17 



... 



26 



3° 



68 



35 



January 16, iqi8 



88 



February 4 

















39 



* 



83 



92 





February 28 



19 

 40 



50 

 67 











92 

 IOO 







March 5 



77 



85 



95 



97 

























Seeds after-ripened out of doors and at 5 C. are more vigorous 

 than seeds after-ripened at slightly higher temperatures (io° C). 

 Dry stored seeds at low temperatures are more vigorous when 

 after-ripened than seeds previously dry stored at high tempera- 

 tures. This question of vigor should be given more attention than 

 it has been given up to the present time. There is something very 

 significant in the fact that maximum vigor can be obtained by 

 after-ripening seeds at a temperature so much below the optimum 

 germination temperature and at a temperature which we consider 

 retarding to metabolic activity in general. Poor germination and 

 high seedling mortality can be replaced by good germination and 

 vigorous seedlings when the most favorable temperature (about 

 5 C.) and water relations are used for after- ripening. After- 

 ripening and germination is a continuous process, but the 

 optimum temperature for germination is considerably above the 

 optimum for after-ripening. Seeds completely after-ripened at 

 5 C. are stimulated to very rapid growth when placed at higher 

 temperatures. On the other hand, if seeds are completely after- 

 ripened and then allowed to desiccate at higher temperatures, 

 seedling vigor is lowered as time progresses, and in several weeks the 



