iqiq] HAAS— respiration 349 



(6 cc.) was placed in each of the tubes. The tubes were clamped 

 shut in such a way as to include a very small air bubble (always 

 of the same size) which served as a stirrer. This was sufficiently 

 accurate and was more convenient than paraffined glass beads. 

 After a tube had been in the dark at i6=t i°C. for a definite period, 

 it was removed from the bath, and the contents shaken by inverting 

 the tube several times. The sea water was then poured rapidly 

 into an empty tube of equal diameter, to which the same quantity 

 (3 drops of 0.0 1 per cent aqueous phenolsulphone phthalein to 

 6 cc. of solution) of indicator was added as had been added to the 

 buffer mixtures. The color was then compared with the colors of 

 a series of buft'er mixtures by the use of a constant source of light 

 (the "Daylight" lamp) and the PH value determined. The same 

 amount of sea water was again added to the tissue in the tube and 

 the tube exposed (at i6=ti°C. in the dark) for the same length of 

 time as before, after which it was removed from the bath and the 

 PH value again determined. This was repeated until the respiration 

 in sea water was approximately constant. Then sea water con- 

 taining the killing agent was substituted for the sea water, and the 

 PH values determined as before after a series of successive periods 

 (each of the same length as the original). 



In some cases (acetone 17.4 and alcohol 24 . 2 per cent) the 

 kilKng agent extracted from the plant a small amount of pigment 

 which interfered with the color of the indicator.^ This difficulty 

 disappeared after the first two periods, however, as was shown by 

 running pure hydrogen through the solution, after which it returned 

 to the color found in normal sea water containing indicator. This 

 method also showed conclusively that the only acid excreted by 

 the plant was carbonic acid. 



The methods of kiUing the tissue were various. Sea water 

 containing anesthetics (made up to the conductivity of sea water 

 by the addition of concentrated sea water) was employed in many 

 of the experiments. In this case the respiration was determined 

 for several periods of equal length in sea water (the solution being 

 renewed after each period). The sea water was then replaced by 



^ This did not occur with low concentrations of these substances. 



