191 9 



Gail; on Fucus avd H t/drogen Ion 



297 



temperature. With a few exceptions there is a gradual decrease in the 

 number of living sporelings as the temperature becomes higher than 

 17°C. The percentage of living sporelings is very small when the tem- 

 perature reaches 30 °C. The maximum number is nearly always found 

 in water having pH values of 8.0 to 8.2. For a graphic representation 

 see plate 51. 



Table 3. Percent of living sporelings at the end of ^ weeks, in different 



temperatures and pH values 



The size of the sporelings growing in seawater having the various 

 pH values and a temperature ranging from 11°-17°C were recorded 

 at frequent intervals. Both the length and the width of the sporelings 

 were measured. The increase in width is very small during this period 

 of growth and will be considered later in this article. Each measure- 

 ment recorded represents the average length and width of 12 typical 

 sporelings. Very little groAvth occurred in seawater having a pH value 

 of 6.6. The sporelings were still alive at the end of four weeks, as they 

 increased in length from 0.104 mm to 0.16 mm when the pH value of the 

 sea water was raised from 6.6 to 7.4. 



The growth of sporelings in seawater having pH values of 7.0 and 

 7.2 was almost completely inhibited after the eighth day. 



The growth in seawater having pH values of 7.4, 7.6 and 7.8 was 

 very much the same. Growth was inhibited to some extent after about 

 two weeks. 



No inhibition of growth is apparent in seawater having pH values 

 of 8.0-8.2. Numerous sets of experiments showed the same results 

 in all temperatures tried below 24°C. The sporelings increased in length 

 from 0.072 mm to 0.192 mm in 72 liours. This was an increase of .12 

 mm. By the eighth day the length was 0.404 mm. Growth continued 

 Ihruout the period. 



