November 9, 1917] 



SCIENCE 



463 



The writer lias recently been able to develop 

 a method^ for the measurement of minute 

 amounts of carbon dioxide. The application 

 of this method to the present problem, has 

 yielded interesting results. 



The experiments veere made by measuring 

 the change in the hydrogen-ion concentration 

 of sea-water produced by the respiration of 

 the marine alga, Laminaria. This was con- 

 veniently done by the addition of a suitable 

 indicator (phenosulphonephthalein) to the sea- 

 water and comparing the color of the solution 

 with the colors of a series of buffer solutions 

 of known hydrogen-ion concentration (con- 

 taining the same concentration of indicator). 



"When the concentration of the anesthetic 

 was so great as to cause considerable dilution 

 of the sea water, concentrated sea water was 

 added until the mixture had the same elec- 

 trical conductivity as sea-water. When an 

 anesthetic (as formaldehyde) showed an un- 

 usually high acidity, the free acid was first 

 neutralized with sodium carbonate. This is 

 allowable for the purposes of the present in- 

 vestigation, as its only effect would be to make 

 the amount of CO^ produced appear somewhat 

 less than was actually the case. By selection 

 of sea-water from different carboys, sea-water 

 could be obtained for controls that had the 

 same PH value as that of the sea-water con- 

 taining the anesthetic. 



The fronds were cut up into pieces about 

 two inches long, the cutting being reduced to 

 a minimum, since it is known that an increase 

 of respiration may foUow injury.^ Prelimi- 

 nary experiments, in which imcut smaller 

 fronds were used for comparison with the cut 

 fronds, showed that the change in the respira- 

 tion due to the cutting was negligible (espe- 

 cially since the cut pieces were usually left 

 about half an hour in sea-water before being 

 used). 



Each piece of tissue was inserted into a 

 Pyrex glass tube, closed by fusion at one end, 

 a piece of paraffined rubber tubing being at- 

 tached to the open end. Sea-water was then 



s Haas, A. E., Science, N. S., 44: 105, 1916. 

 * Cf. Eichards, H. M., Annals of Bot., 10 : 551, 

 1896; ibid., 11: 29, 1897. 



added, the solutions being the same tempera- 

 ture as the bath. The temperature of the 

 bath was always kept at 16° C. Black- 

 enamelled collapsible tin tubes served to ex- 

 clude light from the tubes. After the sea- 

 water bathing the tissue had been changed 

 several times, a given amount of sea-water was 

 added to the tube and a small bubble of air 

 was included in order to serve as a stirrer (it 

 was found to be preferable to paraffined glass 

 beads). After the tube had been kept in the 

 dark at 16° C. for a definite period it was re- 

 moved from the bath and stirred by inverting 

 the tube a few times. The clamp was then 

 opened and the solution rapidly poured into • 

 an empty tube, to which the same number of 

 drops of indicator had been added as was 

 added to the buffer solutions. The solution 

 was then mixed with the indicator in the man- 

 ner just described and the color was then com- 

 pared with buffer solutions of a known PH 

 value (containing the same concentration of 

 indicator). The decrease in PH as observed 

 with a constant source of light ("Daylight" 

 lamp) served to measure the amount of 00, 

 produced by respiration. 



In order to be sure that no acid except CO, 

 was being given off by the plant a stream of 

 hydrogen was allowed to bubble through the 

 solution which had been made acid by respira- 

 tion in order to see whether it came back to 

 the same PH value as at the start.'* This was 

 the case in every instance. 



Each piece of material was used for a num- 

 ber of periods (always of the same length) in 

 sea-water (which was changed at the end of 

 each period) until the rate of respiration had 

 become practically constant. Then several of 

 the pieces were used as controls while others 

 were placed in sea-water containing the an- 

 esthetic (the solutions were always renewed at 

 the end of each period). 



Experiments were carried on with sea-water 

 containing the following substances: .1 per 

 cent, chloral hydrate, .1 per cent, novocain, 1 



5 In very strong concentrations (alcohol 24 per 

 cent, or acetone 17 per cent.) a little pigment may 

 be extracted from the plant. In this case it may be 

 necessary to reject the figures for the first period 

 (or of the first two periods). 



