144 



Pub. Puget Sound Biol. Sta. 



Vol. 2, No. 43 



At the end of three weeks the plants below 12 dm. had a dark color; the 

 plants above this showed little change at this time. At the end of four 

 weeks the younger portions of the plants below 12 dm. were dropping off, 

 leaving only the half decomposed bases. The plants above 12 dm. still 

 had some of the younger portions adhering at the end of nearly six weeks ; 

 but no growth had taken place, and many of the younger parts were easily 

 shaken from the older portions of the plants. On three cords, no 

 young portions of the plants were adhering to the bases after five weeks. 

 On the fourth cord young portions of the plants were found adhering to 

 the older parts at a depth of 1.5 meters. All the cords were suspended 

 within a radius of 10 feet, and conditions were seemingly uniform. Two 

 plants at a distance of 1 m., three plants at a distance of about 4.5 meters, 

 and five at a distance of about 6 meters or more below the surface of the 

 water, had become decomposed at the hold-fast or just above it, and the 

 plants were lost. Table 2 is a summary of these results. 



Table 2. Fucus tvith natural attachment suspended in the sea 

 at different depths 



These plants were submerged all of the time, since the cords were 

 suspended from floating logs. Had all plants been affected as soon and 

 in the same manner, the cause might be submersion. However, since the 

 plants in the deeper water were affected first, and to a much greater de- 

 gree than those nearer the surface of the water, the writer considers that 

 light is at least a much greater factor than mere submergence. It couldn't 

 be temperature, for the difference from surface down is only a few de- 

 grees, and this same species persists on rocks until well into the winter, 

 I am told. It could hardly be COo, for the movement of the water, special- 

 ly about rocky shores in tidal streams would distribute the CO" rather 

 thoroughly. It might be that bacteria would be more effective in darker 

 regions ; however, that again refers it to light. 



Considering that sporelings might be affected more than were older 

 plants, the following series of experiments was not set up for observation: 



1. Sporelings constantly submerged, but under different light in- 

 tensities. 



