NOTES ON NEREOCYSTIS 87 



to adjust itself to the depth of the water, mature specimens being 

 frequently found in shallow water with the normal size of bulb 

 and length of fronds, but with the stipe not exceeding 1 m. in 

 length. 



Nereocystis, as Frye and Setchell have observed, thrives in 

 strong tideways. The writer has never found specimens of the 

 plant growing in quiet water and has never seen any record of 

 such being the case. Frye suggests that the moving water facil- 

 itates the exchange of gases. Submerged plants must, of course, 

 get their oxygen for respiration and their carbon dioxide for the 

 manufacture of carbohydrate food from the gases in the water. 

 The need for these gases is great in the case of rapidly growing 

 kelps and there is of course more gas in water disturbed by wind 

 or tidal currents than there is in quiet water. As Frye observes, 

 moving water facilitates gas exchange by carrying away that 

 laden with evolved gases and lacking in the gases required. 



A rocky bottom seems to be a necessary condition for the pro- 

 duction of kelp beds in the Puget Sound region. The writer has 

 never found this species attached to smooth stones such as Cyma- 

 thaere fastens upon, but always to irregular pieces of rock. 

 This agrees with the observation of Frye. Neither has he ever 

 found it attached to other algae. Setchell has found Nereo- 

 cystis attached to stones and in some cases to the stipes of Ptery- 

 gophora californica. The distribution of the latter species is 

 very limited in the region investigated by the writer of this paper. 

 He found it in the vicinity of Neah Bay only. The writer has 

 frequently found other plants depending upon Nereocystis, but 

 has never found Nereocystis depending upon any other plant. 

 Costaria is quite commonly found anchored to the holdfast of this 

 plant, Antithamnion and other red algae and Desmarestia and 

 other brown algae to its stipe and pneumatocyst. All of the spe- 

 cies epiphytic upon Nereocystis in the Puget Sound region are 

 weaker than it in both holdfast and stipe. Pterygophora has a 

 much stronger stipe than Nereocystis has and it has a powerful 

 holdfast. The writer has not had sufficient experience with this 

 species to make a positive statement about the relative power of 

 its holdfast as compared with that of Nereocystis. 



