146 ' BOTANICAL GAZETTE [February 



Respiration 



A 



the lower temperatures may help to interpret the metabolic activity 

 accompanying after-ripening. Little work has been done on this 

 phase up to the present time. Preliminary tests show very little 

 respiration taking place in dormant air-dry seeds. When these 

 seeds are soaked for 48 hours, however, and then transferred to the 

 respirometer, the respiratory intensity jumps to approximately the 

 same level as that of fully after-ripened seeds. Sufficient data 

 have not been obtained to justify a full discussion of the correlation 

 between after-ripening and respiration. 



Hydrogen ion concentration 



The gas chain method described by Michaelis (18) was used 

 to determine the hydrogen ion concentration. Two embryos 

 were used in each case. They were ground for 2 minutes with a 

 small amount of pure quartz sand and 1 cc. of distilled water, and 

 5 cc. of distilled water was then added. This solution becomes 

 more alkaline the longer it stands, so several readings were taken 

 immediately and the average of these used. In both the dormant 



■ 



and after-ripened embryo we find a distinctly basic condition. 

 The average of several samples shows a P H value of 8 .335 in the 

 dormant seeds and a P H value of 7 . 909 in the after-ripened seeds. 

 Both are distinctly on the basic side of the neutral point. The 

 hypocotyls of the dormant seeds gave a P H value of 9.048, while 

 that of the germinating seedlings with a 1 cm. hypocotyl gave a 

 P H value of 9 .055. Seeds that had just started to germinate were 

 used in the latter case, to be sure that the period of after-ripening 

 had been completed. Eckerson (ii) found increased acidity in 

 the hypocotyl of the haw with after-ripening. In working with 

 Tilia americana Rose (22) found increased hydrogen ion concentra- 

 tion with after-ripening. In the sugar maple the embryo is always 

 basic, although the hydrogen ion may increase in concentration in 

 the embryo when it after-ripens. 



Discussion 



time little work has been done upon seeds that 

 e same type of behavior as found in the river 



