26 Puget Sound Marine Sta. Pub. Vol. 1, No. 5 



From the foregoing then it has been generally conceded, though often 

 questioned, that the gas contained in the large air chambers of many 

 brown seaweeds is an oxygen-nitrogen mixture. Contrary to this opinion 

 we felt that this had not been satisfactorily determined and that the gas 

 might be the result of the metabolic activities of the plant. 



In terrestrial plants the air spaces of the leaves play a definite 

 role in the ready diffusion of oxygen and carbon dioxid to and from the 

 ehlorenchymous tissues in the processes of respiration and photosynthesis. 

 In water plants we generally find these air spaces increased in size. 

 Nereocystis luetkeana (Mertens) P. & R. has a large chamber in which 

 the evolved gases collect, and thus there is no doubt that it is due to this 

 large pneumatocyst that the bulk of the plant is floated in the surface 

 water so that the laminae are exposed to a maximum light. Usually 

 buoyancy is the function attributed to these large accumulations of gas in 

 marine algae (3, 5, 6). The cavity of the pneumatocyst is about 6 to 8 

 feet in length and from 1.5 to 2.0 inches in diameter below the bulb, 

 from which it tapers to a point in the stipe. The cavity of the terminal 

 bulb itself is generally from 4 to 5 inches in length and from 2 to 3 

 inches in diameter. In some specimens the bulb is no larger in diameter 

 than that portion of the pneumatocyst just below the bulb. The capacity 

 of an average sized pneumatocyst is approximately from 3 to 4 liters. 



The work which is reported in this paper was undertaken to obtain 

 definite data concerning the constituents of the gas content of the 

 pneumatocyst of Nereocystis, with special reference to the variation in 

 the amounts of carbon dioxid and oxygen during day and night. In this 

 way it was hoped that we could arrive at some more definite conclusions 

 concerning (1) the function of the pneumatocyst, (2) the source of tne 

 gases concerned and (3) the metabolic activity of marine forms which 

 exhibit such enormous annual growth. 



In 1907 Dr. T. C. Frye of the University of Washington collected 

 the gas of Nereocystis with a view to having it analyzed at the department 

 of chemistry. This, however, was not successful. During the summer 

 of 1911 an attempt was made by one of us to analyze this gas at the 

 Marine Station. This proved fruitless because the type of apparatus used 

 at that time was unsatisfactory. The writers undertook the problem in 

 the summer of 1914, using the Hempel Apparatus for Gas Analysis. 

 The parts used consisted of the modified Wrinkler Gas Burette, a simple 

 absorption pipette for carbon dioxid, and a double absorption pipette for 

 oxygen (4). Alkaline pyrogallol was used as an oxygen absorbent and a 

 solution of potassium hydroxid for the absorption of carbon dioxid. The 

 remainder of the gas after oxygen and carbon dioxid were absorbed was 

 not further tested, but considered as nitrogen. 



