LITTORAL algae; OF PUGET SOUND 97 



posure is as great here as elsewhere. Rigg (4) mentions the fact 

 that certain kelps show a variation in thickness and other features 

 of form, coordinate with different degrees of exposure to violence 

 of waves. Whether the dark brown color of the topmost plants, as 

 contrasted with the yellowish tinge of the lower ones could be 

 a color adaptation was not considered. 



Setchell (6) mentions this color variation in kelps with increase 

 of depth but does not offer any explanation nor suggest any idea 

 of adaptation. Blackman (i) however, agrees with Gaidukov in 

 the notion that the yellow color found in deeper waters is a chro- 

 matic adaptation to the complementary color of the rays coming 

 through the blue water. 



The problem of Prionitis, then, seems not to be so much the 

 procuring of greater light and a warmer temperature but the supply 

 and exchange of gases. In the pools the plants could attach them- 

 selves to the bottom as well as to the margin; but air and pre- 

 sumably CO2 are not available at the bottom. So it seems that 

 the small plants must begin life and the adults continue to remain 

 around the margins, where gases are available and to do this must 

 adapt themselves to a life of exposure on the one hand by increased 

 dissection of the fronds, increased toughness and darker color and 

 diminished size while the opposite of these are suited to a sheltered 

 Hfe. 



CONCLUSION. 



1. Prionitis is adapted to a considerable range of tempera- 

 ture, but seems to prefer the warmer places. 



2. Rhodomela is adapted to nearly as wide a range of tem- 

 perature, but seems to prefer the cooler places. 



3. Both seek protected nooks and pools. 



4. The problem of Prionitis seems to be that of food (CO2) 

 and shelter rather than of heat and light. 



LITERATURE. 



1. Blackman, F. F. Chromatic adaptation. New Phytolo- 

 gist 3: 237-242. 1904. 



2. Chambers, C. O. The relation of algae to dissolved oxygen 

 and carbon dioxide. Ann. Report Mo. Bot. Garden 23: 

 171-207. 1912. 



3. Henkel, Isabel. A study of the tide pools on the west 



