CSi«^ 



24 



If- 



STUDIES IN PLANT RESPIRATION AND PHOTOSYNTHESIS. 



an inverted glass crystallizing dish and over this a galvanized- 

 iron cover. As a seal, the trough contains mercury about 3 cm. 

 deep and over this is placed water. In order to protect the 

 trough and metal cover against the action of the mercury, these 

 were first electroplated with copper, then covered with nickel, and 

 finally given a coat of waterproof lacquer. When the respiration 

 chamber is in use it is entirely covered by the water of the thermostat 

 and quickly attains the temperature of the bath. The metal cover 



Figure 2. 

 Apparatus for automatically changing the course of the air-stream from one absorbing tube 

 to another. The bell-valve with mercury seal is opened by means of the electromagnetic coil 

 and closed when the current is cut out of the coil. One valve is attached to each coil. In the 

 cut, one complete valve connected with the electromagnet which controls it is shown; the three 

 other coils are indicated. 



can be removed during the course of an experiment to observe the 

 leaves in the chamber or to admit light, as the glass cover in the 

 mercury makes an absolutely tight seal. 



On the bottom of the chamber is a glass dish containing a large 

 number of short pieces of glass tubing set on end. This dish contains 

 the nutrient solution and the glass tubes are of a size to admit easily 



