

case were these new roots observed to start from any part 

 of the original root system and in no case was any part 

 of the original root-system found to be still alive. The 

 new root-system formed on the re-admission of o::ygen was 

 found, in every case, to be composed of a few long and 

 thin roots, very little branched. The normal root-system, 

 on the other hand, is much branded and the individual 

 roots are relatively much thicker and shorter. It is 

 by no means certain, however, that this difference in 

 the appearance of the old and new root systems has any 

 relation to the o::ygen supply. More uniform water con- 

 ditions, the absence of light, or the lack of mechanical 

 stimuli to the roots in plants the stems of which were 

 rigidly supported by the seal, may be sufficient to 

 account for these differences. In the two cases in which 

 the oxygen was removed a second time (after recovery from 

 the previous injury) the new root system was formed as 

 befote, but the roots of this new system were also in- 

 jtired and discolored precisely as in the cases of in- 

 jury to ordinary roots. 



In one case a mixture of 50 percent carbon 

 dioxide and 50 percent oxygen (by volume) was ai ied 

 to the roots. The plant was slightly wilted after 7 days 

 and badly wilted after 11 days. However the water- 

 intake did not cease as in the plants supplied only 

 with nitrogen. On examining the root-system it was 

 found to be dead throughout there being no visible evi- 



