1919 Gail; on Fuciis and Hydrogen Ion 291 



ciently heavy to hold them in place, and they were less difficult to find 

 than among the Ulva. There were six rocks bearing the 2-4-lobed Fucus 

 plants and the same number bearing the more mature plants among 

 the Ulva. The same number of each kind were placed in the Fucus beds. 

 All were placed about 1.5 meters vertically above the — 1 tide line. 



After three weeks both the young and mature Fucus plants placed 

 among the Ulva had become much darker in color, and by the end of 4.5 

 weeks they had a decidedly reddish tinge. This is an abnormal color. 

 At the end of 11 Aveeks the reddish tinge was still present except for a 

 space of 3.5 mm around the tip ends and margin of the thallus where they 

 were very dark thruout. A microscopic examination of sections thru the 

 thallus showed a very evident gradient of susceptibility. The cells at the 

 margin were dark brown in color and the walls were in a state of collapse. 

 A little farther in they were still intact but the protoplasm was very dark. 

 In cells still farther in, the protoplasm was more normal in color and 

 normal chloroplasts could be detected. The plants had the same number 

 of lobes that they had in the beginning of the experiment. Measurements 

 showed that on the average they had not increased in size. 



Both the young and the mature plants placed in the Fucus beds had 

 normal color at the end of 1 1 -weeks. The young plants placed in the 

 Fucus bed had groAvn to twice the size of the young plants placed among 

 the Ulva. A microscopic examination showed the cells to be normal. 



The average pH value of the water about the Ulva at about 6:00 A. 

 M. was 7.85, and at about 2:00 P. M. was 8.72. The average pH value 

 of the water about Fucus at about 6:00 A. M. was 7.88, and at about 

 2:00 P. M. was 8.21. The average temperature of the water among 

 the Ulva was 13° C at about 2:00 P. M. The average lower extreme was 

 11° C. The light was of the same intensity since they were the same 

 distance above a — 1 tide and were on the same exposure. All conditions 

 seemed to be the same except that of the pH value of the water. The dif- 

 ference in growth and color in this experiment points toward the difference 

 in the pH values of the water in the two locations, as a means by which 

 the presence of Ulva may limit the distribution of Fucus. 



Effect of pH ano temperature on young plants 



Experiments were started to study the effect on P\icus plants of pH 

 values on the acid side of true neutrality and on u}) thru the higher alka- 

 line values. 



Open 4-liter glass jars were used, and three liters of water were 

 used in each jar. The water was taken from the Sound, away from visible 

 vegetation. It had an average pll value of 8.05. Commencing with pH 

 value of 6.6 each jar was labeled respectively 6.8, 7.0, 7.2, etc., thru 8.8. 



