1919] HAAS— RESPIRATION 383 



pieces of material in normal sea water until constant values for 

 the respiration were obtained; then sea water diluted with 10 

 per cent of tap water was used, and it was found that the dilution 

 produced no appreciable effect. 



In each experiment 6 cc. of solution was used. At the end of 

 each period, after noting the new PH value, 6 cc. of fresh solution 

 was poured into the tube, which was then treated as before. It 

 was at first thought that in pouring out the solution from the tube 

 containing the tissue sufficient might be held back by the tissue 

 to affect the observed PH value. Actual determinations proved 

 that this was not the case. 



In view of the fact that there may be an increase of respiration 

 as the result of injury (23), preliminary experiments were made to 

 ascertain whether the cutting of the Laminaria had any appre- 

 ciable effect upon the respiration. It was found that the change in 

 the respiration due to cutting was negligible (the cutting was always 

 reduced to a minimum). 



In some of the experiments there was noted a very slight decrease 

 in the production of CO2 as time went on, although not enough to 

 be of significance for the present investigation. This phenomenon 

 has been observed by Miss Matth.a.ei (17) in determinations of 

 CO2 in connection with experiments on photosynthesis. Such a 

 decrease in respiration has been attributed by her to the gradual 

 decrease of substances available for oxidation. 



The results of the experiments are given both in tables and 

 figures. In each experiment 6-12 (or more) closely agreeing deter- 

 minations were obtained and the results of a typical case were 

 taken. The plant was always placed for a definite time in sea 

 water or sea water containing the reagent, and at the end of this 

 time the PH value was determined. This interval is in every case 

 shown in the tables as well as by the points on the curves. At the 

 end of each interval the solution was renewed. 



The alteration of the PH value is an index of the amount of 

 CO, produced, since the greater the amount of CO^ the greater 

 the decrease in PH. Since this relation is approximately linear in 

 this range of PH values, it is not necessary to translate the decrease 

 in PH value into cc. of CO2 produced, as the form of the respiration 



