206 STUDIES ON EESPIRATION. IV 



.was followed by a more gradual fall which reached the normal rate in 

 43 minutes and continued to fall, so that at the end of 90 minutes 

 the rate was only 60 per cent of the normal. 



Some experiments were made to determine the recovery after ex- 

 posure to 7.3 per cent ether for periods of various lengths. This was 

 done by putting the seeds in large Petri dishes to germinate. It was 

 found that the seeds would not recover if the period of exposure 

 was greater than 30 minutes. Short exposures (up to 8 minutes) 

 were stimulating, for growth was more rapid than the normal growth 

 of unexposed seeds, but any exposures beyond 8 minutes resulted in 

 a decreased rate of growth up to 30 minutes, after which there was 

 no recovery. During the period from 30 minutes to 43 minutes, 

 the curve shows that respiration is above normal, but the seeds 

 would not recover. This was probably due in part to rapid respira- 

 tion after death, such as Haas^^ found in Laminaria, but it should 

 not be inferred that death took place at the end of 35 minutes be- 

 cause no recovery was possible after this period. It is more prob- 

 able that the seeds were alive at the end of 35 minutes and that 

 death occurred after removal from the ether solution. 



In the experiments in which 3.65 per cent ether solutions were used 

 there was an immediate increase which reached the maximum of 

 178 per cent (78 per cent increase) in 13 minutes (Fig. 1, Curve B). 

 This increase was followed by a more gradual fall which reached the 

 normal rate in 1 hour, and then fell still more gradually below normal 

 so that at the end of 140 minutes the respiration was only 81 per cent 

 of the normal. In all experiments with 3.65 per cent ether the seeds 

 showed by the germination test that the anesthetic "did not cause 

 death, even after an exposure of 12 hours. 



The 3.65 per cent ether caused a more gradual rise and fall in the 

 rate of respiration than the 7.3 per cent ether and the increase was not 

 so great. In both cases, however, there was a definite rise followed 

 by a fall. 



In 0.73 per cent ether the rise was less than in 3.65 per cent and re- 

 covery was possible even after an exposure of 12 hours. 



12 Haas, A. R. C, Proc. Nat. Acad. Sc, 1917, iii, 688. 



