CHAPTER IX. 

 RESPIRATION. 



125. One of the life processes in plants which is extremely 

 interesting, and which is exactly the same as one of the life pro- 

 cesses of animals, is easily demonstrated in se\eral ways. 



126. To set up the apparatus for demonstrating respiration. — Soak a 

 double handful of peas for 12 to 24 hours in an abundance of cool water. 

 Prepare a small quantity of baryta water, a saturated solution, and filter some 

 into a short wide vial. Take a glass cylinder about 35 cm high by 5 cm in 

 diameter. Select a perforated rubber cork to fit very tightly when crowded 

 part way in the open end of the cylinder. Prepare a long S manometer by 

 bending a glass tube, which is about one and one half meters long by 6 mm 

 inside diameter, into the form shown in figure 4.611. Put mercury into one end 

 of the manometer as shown in the figure, and if it is desired to show the experi- 

 ment at a distance in the classroom, place a small quantity of a solution of 

 eosin above each column of mercury. Insert the other end of the manometer 

 through the perforation in the rubber cork. It must fit very tightly. If there 

 is another perforation, plug it with a glass rod. 



Take a wide-mouth glass jar (a small glycerine-jelly jar is good) which will 

 go inside the cylinder. Break a few sticks of caustic potash and drop into it. 

 Nearly fill with water, and tie a string around the upper end so that it can be 

 lowered in the upper part of the cylinder without spilling any of the potash 

 solution. Prepare a support for this by inserting a glass rod about 13 cm long 

 into a small cork. Have all the parts of the apparatus aud the material ready, 

 and the baryta water in the open vial, so that the apparatus may be set up 

 quickly. Have the cylinder warm, and set the apparatus up in a room where 

 the temperature is about 20° C. (about 68° Fahr.). Place a small quantity of 

 damp paper (not wet) in the bottom of the cylinder. Place in the soaked peas 

 to fill about 8 cm to 10 cm. Upon these place the small vial of baryta water. 

 Drop in the support and press the glass rod down far enough so that the jar of 

 potash solution will enter and pass below the rubber cork. 



Insert the rubber cork containing the S manometer of mercury, placing be- 

 tween it and the side of the cylinder a stout needle to allow the escape of air 



53 



