292 Pub. Puget Sound Biol. Sta. Vol. 2, No. 51 



The correct pH value from 6.6 to 8.0 was secured by the addition of HCl. 

 From 8.2 thru 8.8 the correct pH value was secured by the addition of 

 sufficient amounts of water from about Ulva. When the tide was high it 

 was necessary to add NaOH in place of water taken from about Ulva. 

 In the addition of both the HCl and NaOH a medicine dropper was used. 

 The indicator used for testing the pH values was phenolsulphonphthalein. 

 The hydrogen ion set was used wholly for the comparison of colors. In those 

 cases in which the pH values ranged from 6.6 to 8.0 it was necessary to make 

 the pH corrections of the water nearly every hour of the day. The number of 

 changes necessary depended largel}^ upon the intensity of the sunlight. 

 The correction of the pH values above 8.0 was necessary two or three 

 times per day depending also upon the intensity of the sunlight. These 

 changes kept the pH values of the water reasonably accurate. The sea- 

 water was changed completely in each jar once each day. 



The temperature of the water in two of the sets of the experiment 

 varied from 11° C to 24° C, These were the temperatures secured on the 

 float where the jars remained during the time of the experiment. The 

 temiaerature of the water in the third set varied from 10.5° to 13° C. 

 This temperature was obtained by suspending in the Sound trays with 

 bottoms of wire netting. The trays were fastened by cords between two 

 logs on a float. The jars were placed in the trays. The trays were regu- 

 lated in such a manner that the surface of the water in the jars had the 

 same level as the surface of the water of the Sound. The lower tempera- 

 ture, 10.5° C, was the average temperature of the water in the jars at 

 night. The higher temperature, 13° C, was the usual temj^erature at about 

 1:00 P. M., which was about 1° C higher than the temperature of the 

 Sound at that time. Two-lobed young Fucus plants with natural attach- 

 ments were used. Three such sets were continued over a period of nearly 

 1 1 weeks. All conditions were the same except that of temperature. 



The results of the two sets having the temperatures range from 11° C 

 to 24° C will be considered first. The Fucus plants in the seawater having 

 a pH value of 6.6 and 6.8 lived about 9 days. The thalli of the plants 

 commenced to curl on the second day. They showed signs of whiteness 

 about the margins on the third day. On the fifth day the larger portion of 

 the entire thallus looked whitish and soft. A microscopic examination of 

 the cells on the seventh day showed those near the tips and margins to be 

 completely broken down. The cells a little farther in were very much 

 plasmolyzed. Still farther in, a few of the cells were apparently normal. 

 No cells were normal on the ninth day. Here also the gradient of suscep- 

 tibility is well shown. These plants were kept two weeks longer in the 

 seawater having their respective pH valvies. At the end of this time 



