Gas Exchange in the Pneumatocyst of Nereocystis 

 luetkeana (Mertens) P. & R. 



Sanford Myron Zeller, 



Missouri Botanical Garden, St. Louis 



and 



Abigail Neikirk, 



University of Washington, Seattle. 



The chemical composition of the gas in the air chambers of certain 

 marine algae, chiefly those belonging to the Fucaceae and Laminariaceae, 

 lias long been a question of considerable interest. As early as 1868 

 Rosanoff (7) had made observations on the gas evolved from certain 

 marine algae. The gas collected from the aeriferous vesicles of Fucus 

 vesiculosus consisted of pure nitrogen with no trace of oxygen or carbon 

 dioxid. 



In 1889 Willie (8) found that there is a variation in the oxygen 

 content of the air chambers of some of the Fucaceae. In plants which 

 Avere submerged at high tide he found from 35 to 37 per cent of oxygen 

 in the day time but after being exposed to the air for 10 hours the oxygen 

 was reduced to 20.7 — 20.8 per cent or practically that found in ordinary 

 •lir. After remaining in the dark for 12 hours the oxygen was reduced 

 to 2.7 per cent. Carbon dioxid was always completely lacking. 



In 1911 Lucas (5) made analyses of the gases in the vesicles of 

 Phyllospora comosa, Hormosira banksii, and Cystophora monilifera. The 

 plants used were not the normally growing plants but were fresh-looking 

 plants which had been cast upon shore or were floating free in the sea. 

 His experiments showed that oxygen and nitrogen were present but he 

 detected no carbon dioxid. Lucas outlines three possible sources of the 

 gas: (1) atmospheric air, (2) gases produced in the metabolism of the 

 plants themselves and (3) the gases dissolved in the sea water. Since 

 he detected no carbon dioxid in the floats and since any process of 

 metabolism would evolve carbon dioxide, he concludes that the gases are 

 the result of osmosis through the plant tissues from the water. Since 

 however his analyses for "sea water gas" show from 6 to 11 percent 

 of carbon dioxid and since carbon dioxid diffuses and osmoses more rapidly 

 than oxygen, and the latter more rapidly than nitrogen, we cannot con- 

 ceive of the absorption of oxygen and nitrogen and the entire exclusion 

 of carbon dioxid. 



(25) 



