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PHYSIOLOGY OF NUTRITION. 



R 



FIG. 93. Apparatus for demonstrating the production of Carbon dioxide intb 

 respiration of plants. 



cylinders a and c contain clear baryta water. We 

 treat Barium hydrate in a large flask with distilled 

 water, shake well repeatedly, allow to settle, and after 

 thoroughly drying the cylinders a and c introduce into 

 them a sufficient quantity of the solution by means 

 of a well-dried pipette. The U-tube 6 contains the 

 respiring plant structures (flowers or seedlings). The 

 lower portion of the vessel d contains potash solution, the upper 

 portion fragments of caustic potash. If immediately after putting 

 together the apparatus, we open slightly the stop-cock of the tube 

 jB, water flows from the tube, and a stream of air passes through 

 the whole apparatus. It is deprived of Carbon dioxide in d, and 

 hence the baryta water in c remains clear. The baryta water in 

 a, on the other hand, very rapidly becomes turbid, or a precipitate 

 of Barium carbonate may be thrown down, which proves that 

 Carbon dioxide is produced by the plant material under investiga- 

 tion. 



The following arrangement serves to demonstrate the consump- 

 tion of Oxygen in normal respiration (see Fig. 94). In a wooden 





