igig] 



ROSE— AFTER-RIPENING AND GERMINATION 



291 



determinations were made by the titration method with pheno- 

 phthalein as an indicator. The Ph of seeds with the hypocotyls 

 0.5 cm. to 2 cm. long is approximately 4 times as great as that 

 of the unafter-ripened seeds. While this is not as great an increase 

 as that found by Eckerson, it may be due to the fact that her 

 determinations were made upon the dormant organ alone, while 

 here the whole seed was used, or to differences between the two 

 kinds of seeds. Determinations made by the titration method 

 would also probably give values much higher than those obtained 

 by the hydrogen elctrode. 



Table V shows that the weight of the seeds increases as after- 

 ripening progresses. This is not due to an increase in dry weight, 



TABLE V 



Concentration of hydrogen ion of Tilia seeds in different stages 



OF after-ripening 



Condition of seeds 



1 Air-dry 



2 Air-dry 



3 Air-dry 



4 Air-dr\' 



5 After-ripened 



6 After-ripened 



7 With hypocotyls 5 mm 



8 With hj'pocotyls 5 mm 



9 With h>'pocotyls 5 mm 



10 With hypocotyls 0.5-2 cm 



1 1 With h>-pocotyls o . 5-2 cm , 



i2*With hypocotyls 0.5-2 cm , 



i3*With h>^ocotyls o . 5-2 cm 



i4tWith hypocotyls o . 5-2 cm , 



i5tWith hj-pocotyls o . 5-2 cm 



16 After-ripened at room temperature (10 days) 



1 7 After- ripened at room temperature (10 days) 



2. 24X10-7 

 2.00X10—7 

 2.58X10-7 

 2.40X10—7 

 3.24X10-7 

 3.02X10-7 

 6.76X10-7 

 5.75X10-7 

 7.59X10-7 

 1.18X10-6 

 1. 10X10-^ 

 9-33X10-7 

 9.33X10-7 

 1. 05X10-6 

 1. 05X10-6 

 2.51X10-7 



2. 51X10— 7 



* 50 cc. of water used. 



t loo cc. of water used; 25 cc. of water used for all others. 



since no photosynthesis has taken place, but to the large amount of 

 water absorbed. Eckerson (8) likewise observed an increased 

 water-holding capacity for the hypocotyl of Crataegus as after- 

 ripening progressed. Of greater significance in this connection is 

 the fact that, at least for the most advanced stage of after-ripening, 

 variations in the amount of water used with the sample had Uttle 



