300 Pub. Fuget Sound Biol. Sta. Vol. 2, No. 51 



planted on glass slides and placed in three different glass jars each con- 

 taining two liters of seawater having a pH value of 8.2. The tempera- 

 ture of one jar did not go higher than 13°C. In a second jar it did not 

 go higher than 17°C. In a third jar it did not go above 27°C. Each 

 jar contained two slides and each slide contained over 75 oospores. A 

 95 per cent germination took place in those jars in which the tempera- 

 ture varied from 11° to 17°C. About a 3 per cent germination resulted 

 in those jars in which the temperature went as high as 27 °C, when this 

 high temperature was maintained 2 hours or more. In these experi- 

 ments the desiccation factor was eliminated and the effect of tempera- 

 ture was clearly demonstrated. Undoubtedly desiccation on the beach 

 is harmful to the germination of oospores and the growth of sporelings 

 but the high temperatures often reached may be the determining factor 

 if they continue any considerable length of time. 



Study of tidepools 



A study of tidepools was also made in order to find why Fucus does 

 not grow in them. Chambers (1912) claims that young plants of Prionitis 

 lyallii are always found starting around the rim of tidepools where the 

 COo would supposedly be abundant^ but never on the bottom, where both 

 COo and oxygen would in all probability be absent or much diminished. 

 He believes the whole problem M'ould resolve itself into a question of 

 aeration. The writer has made numerous tests in tidepools and found 

 that the average pH value of the seawater in them between 1 :00 P. M. 

 and 4:00 P. M. was 8.59, and that it was often 8.8. This is partly 

 brought about by the seawater draining from the surrounding Fucus 

 beds into tlie tidepools when the tide is going out. As the seawater 

 makes its wa}^ down into the tidepools, it is continually taking up oxygen 

 and is well aerated. The microscopic algae and Prionitis lyallii also 

 make the water more alkaline in the manufacture of their carbohydrates. 

 During the night COo is liberated largely and oxygen is used in respira- 

 tion. This CO2 unites with HoO, forming H0CO3, which makes the sea- 

 water in the tidepools more acid. The average pH value was 7.43 

 a little before sunrise. The writer has never found a good growth of 

 Fucus in seawater having as high pH values as occur in tidepools during 

 the day nor in seawater having as low pH values as occur in tidepools in 

 the early morning. 



The average temperature of the tidepools between 1 :00 P. M. and 

 1:00 P, M. was 24.7°. This high temperature has already been shown 

 to be harmful to Fucus. When oospores were planted on shells and 

 placed in the tidepools there was less than a 5 per cent germination. 

 Those that did germinate soon became loosened from the shells. The 



