294 Ptib. Puget Sound Biol. Sta. Vol. 2, No. 51 



in seawater liaving a pH value of 6.6, and none until at the end of three 

 weeks on those in 6.8 and 7.0. 



No effects could be seen in 7.2, 7.4 and 7.6 except that growth ap- 

 l>eared somewhat inhibited. In 7.8 there was an average increase in length 

 of 5.5 mm, and some showed the beginning of four lobes. 



The plants in seawater having pH values of 8.0 to 8.2 had on the 

 average the same growth as the plants in the same pH values but with the 

 temperatures ranging from 11° to 24°C. The color, however, was more 

 nearly the same as the color of the Fucus plants of the same age growing 

 on the shore. This wide range of pH values and higher temperature 

 must account to considerable extent for the lighter color of the Fucus 

 plants in the previous set having the same pH values. 



The Fucus plants in the seawater having pH values of 8.4, 8.6 and 

 8.8 were affected in practically the same manner as in the previous set 

 with the higher and wider range of temperature. The period of time 

 necessary to show the same results was from 4 to 6 days longer in this 

 narrow range and lower temperature. 



Percent of germination of oospores 

 Experiments were also undertaken with a view to determining effects 

 both of temperature and of pH values of the seawater on the acid side of 

 true neutrality and on up through the higher alkaline values, upon the 

 germination of oospores and upon the subsequent growth of the sporelings 

 produced. The oospores M'ere obtained in the manner previously described 

 (Gail, 1918). They were germinated on microscopic slides placed in 

 glass jars containing seawater having the different pH values. Four dif- 

 ferent ranges of temperature, 10.5°-13°C, 11°-17°C, 11°-24°C and 11°- 

 30° were used. The temperature of 10.5°-13°C was secured by suspend- 

 ing trays with bottoms of wire netting in the Sound as was previously 

 described. The temperature of 11°-17°C was secured by placing the 

 jars containing the different pH values of seawater in porcelain pans 

 containing seawater, and setting these on a float on the Sound. The 

 pans were about 60 cm high. The water in the pans was changed as 

 often as was necessary to keep the temperature at 17°C or below. The 

 temperature of the seawater having the different pH values usually 

 went down to 11°C at night on the float. The temperature of 11°-24°C 

 was the temperature produced by the atmosphere on the float some dis- 

 tance from the bank. The last temperature, 11°-30°C, was that pro- 

 duced by the atmosphere on the float but near the shore where it was 

 protected from the wind. Each set was run in duplicate. 



The per cent of germination will be considered first. An examina- 

 tion of table 2 will show the following: 



