158 STUDIES ON RESPIRATION. XIX 



root-hairs. The material was used when the roots were from one to 

 one and a half inches long, with abundant surface for absorption and 

 respiration. Before using, the seeds were washed for 10 minutes 

 in running water. They were then put into a fiask of Pyrex gjass, 

 with 100 cc. of distilled water, and the apparatus was allowed to 

 run. After the rate of respiration had become constant (in dis- 

 tilled water) it usually remained so for at least 8 hours. As the 

 average experiment lasted from 2 to 4 hours, it was possible to dis- 

 count any variations in the rate as being due to manipulation, pro- 

 vided that the temperature remained constant. During the course 

 of an experiment the temperature seldom varied more than a degree 

 either way. The average room temperature was 20°C. 



The indicator used was phenolsulfonephthalein in aqueous solution. 

 The normial rate of respiration was taken as the reciprocal of the time 

 required to change the pH value of the indicator from pH 7.36 to 

 pH. 7.09, these values being chosen as being sufficiently different in 

 tint to be easily read. The time varied with the age of the seedlings, 

 ranging between 30 and 60 seconds. 



The seeds were treated with a watery solution of ether, the con- 

 centrations employed being 1 per cent, 3.65 per cent, and 7.3 per cent 

 (by volume). After the rate of respiration had become constant, 

 100 cc. of the required solution was substituted for the distilled water 

 in the flask, and the experiment continued .- 



With a solution of 1 per cent ether in distilled water the first effect 

 was a fall in the rate of respiration. Fig. 1 (average of five experiments) 

 shows that the minimum reached was 36 per cent of the normal, 

 6 minutes after the beginning of exposure to the ether. The rate 

 then rose gradually towards normal, but remained below it for 48 

 minutes. The next stage was a rapid rise to 124 per cent, the maxi- 

 mum being reached in 51 minutes, and the duration above normal 

 being 6 minutes. This was succeeded by a depression, when the 

 rate fell gradually to about 50 per cent in about 4 hours. 



With a solution of ether 3.65 per cent the first effect was the same, 

 the rate reaching a minimum of 48 per cent in 9 minutes. The de- 

 pression lasted for 24 minutes, and was followed by a rapid rise, the 



2 Care was taken to avoid any possible errors due to the admission of air in 

 opening the apparatus or to the introduction of distilled water. 



