4 6 



BOTANICAL GAZETTE 



[JANUARY 



not to changes in the permeability of the coat, as later experiments 

 show. 



Table XII gives the changes of H + ion concentration as P H 

 values for the endosperm and different parts of the embryo during 

 storage at 5 C. The outer cells of the embryo and its hypocotyl 

 were the first parts to show an increased H + ion concentration. 



TABLE XI 



Percentage of water in seeds taken from coats after 

 different periods of exposure to 5° c. 



TABLE XII 



H+ION CONCENTRATION OF SEEDS DURING AFTER-RIPENING* 



Condition 



Diy 



Dry 



After 30 days at 5 C 



After 30 days at 5 C 



After 60 days at 5 C 



After 60 days at 5 C 



After 90 days at 5 C 



After 90 days at 5° C 



After 90 days at 5 C 



After 90 days at 5 C 



* These determinations were made with 



Part of seed 



Endosperm 



Embryo 



Endosperm 



Embryo 



Endosperm 



Embryo 



Embryo hypocotyl 



Endosperm 



Embryo outer cells and hypocotyl 



Embryo inner cells 



4-6.0 

 4-8.8 

 6-5.2 

 8-7.6 

 4-6.0 

 8-7.6 

 0-6.8 

 4-5-2 

 4-5-2 

 6-6.0 



the Clark and Lubs indicators. 



The embryo showed a marked increase of H + ion concentration dur- 

 ing after-ripening, while the endosperm with P H value of 4 . 4 (con- 

 centration of H + ionsXN = o.72Xio — 4 ), being already acid, showed 

 very little change. This may indicate that the embryo is the 

 principal seat of dormancy. Table XIII gives the increase of 

 titratable acid in the endosperm and embryo during after-ripening. 

 The increased acid was determined by titrating with N/50 NaOH, 



