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An Apparatus for Aerating Culture Solutions. 



Paul Weathilrwax. 



A number of experiments on various phases of plant physiology, in each 

 of which it was necessary to secure a constant stream of air continuing for 

 several days, has led to the construction of a very efficient piece of ap- 

 paratus for that purpose. The apparatus used by Prof. D. M. Mottier sev- 

 eral years ago for aerating artificial cultures of algse was modified by F. L. 

 Pickett and used in a series of experiments on desiccation ; and the writer 

 has made some further changes in the construction of the apparatus shown 

 in the figure and described below. This is now being used very success- 

 fully in the aeration of culture solutions. 



The princple employed is that of the Sprengel mercury pump (water 

 being used as a liquid in this case) by which bubbles of air are entangled 

 in a stream of liquid which flows into a closed vessel. The only thing that 

 remains to be done is to separate the air and the liquid, which are under 

 slight pressure, and convey them from the reservoir by separate tubes. 



The first problem is that of getting a stream of water that will flow 

 uniformly. An attachment to a water pipe is usually sufficient for this. 

 If this is not satisfactory, however, a siphon may be arranged to give a 

 uniform flow. D, in the figure, is an ordinary battery jar provided with 

 a siphon, B, which has an adjustable stopcock. A, which taps a water 

 pipe and has an adjustable stopcock, supplies the jar with water a little 

 faster than it is taken out by the sipbon, B. Another siphon, C, removes 

 the excess and keeps the water always at the same level, determined by 

 its outer end, thus assuring an even flow, which should be just fast enough 

 to cause the water to fall as a succession of drops. 



The funnel, E, made by fitting a stopper into the end of a short piece 

 of glass tubing about 1 cm. in diameter, has the end of the slender tube, F, 

 extending 2 or 3 mm. above the cork. By means of this arrangement the 

 water dropping into the funnel is caused to descend through the tube as 

 a series of di-ops separated by spaces filfed with air. Thus, if no escape 

 is allowed, the reservoir, K, is filled with water and air under a pressure 



