298 



METABOLISM ^D Gl.OWTH EST SEEDS 



and another containing dilute .OH and phenol red, and a measure- 

 ment was made of the time required for the liberated CO2 to change 

 the reaction of this solution from pH 7.60 to pH 7.09. The rate of 

 CO2 production per seed was expressed by the reciprocal of this time 

 divided by the number of seeds.^ During the measurement the tube 

 containing the seeds was immersed in a water bath at constant tem- 

 perature, usually at 25°C, 



In order to determine the accuracy of the method, and the varia- 

 tions which would result from measuring different groups of seeds a 

 series of control experiments was performed. In each the seeds were 

 divided into two numerically equal lots, and six or eight successive 

 me£Lsurements made of the CO2 production. Table I shows that the 



TABLE T. 



Comparison of Unradmted Seeds. 



* Method of calculating explained in the text. 



probable error of the mean of the successive measurements on any 

 lot does not exceed as a rule 5 per cent. The percentage difference 

 in measurements of different lots is less than 13 per cent in all but 

 one of the experiments. 



The ability of the seeds to germinate and grow was examined by 

 placing comparable lots of seeds on moist filter paper. They were 

 covered by a large glass vessel to prevent rapid drying, but access of 

 fresh air was not completely cut off. It was found that at least 95 per 

 cent of unradiated seeds germinated and grew under these conditions. 



^ The seeds were weighed in the dry condition and the CO2 production esti- 

 mated per gram of seeds. The relative CO2 productions of different lots of seeds 

 expressed in this way did not differ materially from those obtained by the method 

 employed above. 



