f^ 



The ability of the roots of willow and eucalyptus 

 to survive long periods of oxygen deprivation without ap- 

 parent injury to the plants suggests that these roots 

 may be capable of respiring entirely anaerobically. The 

 data imply that this is true, out the affirmative answer 

 can be given with entire assurance. It is possible! that 

 some small source of oxygen was neglected accidentally 

 or escaped the precautionary expedients of the experiments. 

 It is possible, also, that the traces of oxygen which 

 doubtless remained in the pots at the beginning of the ex- 

 periments may have sufficed for a measure of root respira- 

 tion over the whole period of inclosure. Certainty as to 

 the possible anaerobic life of these or other roots can 

 be reached only by the repetition of the experiments often 

 enough to exclude the possibility of accidental error. In 

 any event there can be no question that Goleust and helio- 

 trope differ markedly from willow and eucalyptus in the 

 amount of oxygen needed by the roots, and that the last 

 named plants require at most only an extremely small 

 amount. On the face of the experiments they require 

 none at all. 



The single experiment on the effect of carbon 

 dioxide on Goleus indicated some specific poisonous action 

 of this gas, but this is obviously not general since there 

 was no effect on willow with a much longer exposure. It 

 is interesting that the application of carbon dioxide to 

 Coleus did not stop the water-intake though it did cause 

 wilting and death. 



