89 



jar and the glass top, .'/haseolus was tested with pure 

 carbon dioxide, with 90 percent carbon dioxide and 10 

 percent air, with 80 percent carbon dioxide and 20 

 percent air, and with hydrogen. With the pure carbon 

 dioxide the plants wilted in from ^ to 1 hour. V/ith 

 carbon dioxide $he wilting occurred in from 1 to 2 

 hours, and with 80 percent carbon dioxide, in from 2 

 to 3 hours* After wilting by exposure to pure carbon 

 dioxide the plants revived if air was passed through 

 from 1 to 1-|- hours. Use of hydrogen instead of carbon 

 dioxide produced iio effect. The total time for which the 

 hydrogen was passed is not stated. Experiments with 

 Yicia and pure carbon dioxide gave substantially the same 

 result except that the wilting occurred only after 3 to 

 4 hours. Hydrogen was again without effect. It is 

 obvious that these experiments, except for the trial 

 of hydrogen, go little beyond the earlier results of 

 Jentys. The negative result with hydrogen also has lit- 

 tle significance for the reason that the time of the ex- 

 periment, although not stated, was probably too short 

 to disclose any effect of root suffocation had one been 

 possible. Hydrogen, in itself, probably has no effect, 

 its only action being to replace the oxygen. 



The experiments in water- culture were made 

 quantitatively, the effect on the rate of water absorp- 

 tion by the roots being measured by determining the 



transpiration from the culture under the various treat- 



