ON THE ORIGIN OF THE GASES IN THE FLOAT OF BLADDER KELP

The problem of determining the presence or absence of microorganisms in the interior of the large cavity (float, or pneumatocyst) present in bladder kelp (Nereocystis) is approached in this paper from the standpoint of its bearing on the metabolism of the plant, especially with reference to the large amount of carbon monoxide present in this cavity. Internal closed cavities of varying sizes are common in plants ranging from seed plants to algae. The large cavities of pumpkins and squashes are familiar. Langdon and Gailey (I920) have tested many such cavities in seed plants and have found neither carbon monoxide nor carbon dioxide in them. Among the kelps of the sea along the Pacific Coast of North America that have gas-containing cavities that serve to buoy up portions of the plant are Nereocystis luetkeana (bladder kelp), Macrocystis pyrif era, Pelagophycus porra (elk kelp), Egregia Meniziesii (feather boa kelp), and Alaria fistullosa. Lucas (I9I2) has also listed the following marine algae that have vesicles filled with gas: Sargassum, Carpophyllum, Turbinaria, Cystophora, Cystoseira, Scaberia, Phyllospora, and Hormnosira. There seem to be four possible sources of gases contained in internal cavities of marine algae: (i) atmospheric air, (2) gases dissolved in sea water, (3) the activities of microorganisms, and (4) the metabolism of the plants themselves. Lucas (I9I2) analyzed the gases from marine algae of several genera and found only nitrogen and oxygen, with the proportion of nitrogen always greater than that in atmospheric air. He rejects atmospheric air as a source of the gases since his analyses show a higher content of nitrogen than is present in the atmosphere and because the gases must be formed in the cavity pari passu with growth; otherwise the vesicles would collapse. He also rejects the metabolism of the plant as a source of the gas because " it is hardly conceivable that any process of metabolism should yield these two gases (nitrogen and oxygen) only without any carbon compounds." He accepts the gases dissolved in the sea water as a source of the gas in the vesicles, and believes that the gas enters, dissolved in the water by osmosis. He reasons by analogy