630 GASES PRESENT IN FLOATS OF CERTAIN MARINE ALG.E, 



the balloons, freshly gathered from the vine. A single balloon 

 yielded over lOc.c. of gas. 



No evidence could be obtained of the presence of carbon 

 dioxide above the amount ordinarily present in air. There was 

 no evident absorption by potash; and though the gas -wbls allowed 

 to stand over lime-water for six hours, not the slightest film of 

 carbonate formed on the surface. 



Three separate determinations of oxygen were made by the 

 phosphorus method. Simultaneously with the third sample of 

 gas, an equal volume (lOc.c.) of air was tested under practically 

 the same conditions of temperature and pressure The results 

 were — 



Gas No. 1. Oxygen 203%. Using graduated vessel A. 



GasNo.2. Oxygen 190%. ,, ,, ,, B. 



GasNo.3. Oxygen 200%. ,, ,, ,, A. 



Air Oxygen 190%. „ ,, „ B. 



It seems plain, then, that the gas is identical with ordinary 

 air, the difference in reading being probably due to the slightly 

 unequal graduations of the two measuring vessels. 



The balloons were of a vivid tender green The outer surface 

 has a distinct epidermis provided with hairs and storaata. 

 There is no inner epidermis, the lining tissue having the 

 same loose structure as that of .the septa dividing the capsule. 

 It is plain, then, that atmospheric air can be admitted under 

 the control of the guard-cells of the stomata, and can pene- 

 trate all the loose tissues of the thin capsule- walls, passing 

 through to the cavity within. As the balloons were gathered in 

 the early morning, it would seem that any free carbon dioxide 

 formed during respiration passes out of the stomata, and does not 

 accumulate inside the capsule. 



The use of the balloons is apparently to allow of the distribu- 

 tion of the capsules by the wind. They are easily detached when 

 ripe, and from their shape can be rolled along the ground as well 

 as carried in the air. And the plant secures the gas necessary 

 for inflation by the readiest means from the handiest supply, i.e., 

 the suri'ounding atmosphere. 



