196 



THE TEACHING BOTANIST 



due to a confusion of it with the gas exchange in photosyn- 

 thesis. There is no place in the cycle of the plant's life in 

 which respiration can be studied so free from complication 

 with other processes as in germinating seeds. 



Experiment No. 3.- -Prepare three U -tubes and three up- 

 right test-tubes, as shown in Fig. 18, or their equivalents. 

 Half fill the test-tubes with, respectively, water, a strong solu- 

 tion of caustic potash, and a concentrated mixture of caustic 

 potash and pyrogallic acid. Place in one arm of each U-tube 

 a half dozen soaked oats, beneath which is a small wad of 



moist Sphagnum, and cork 



S~ ~^ -v 



tightly with rubber stop- 

 pers ; do not allow the 

 arm to become wet above 

 the seeds, or the potash 

 will diffuse over and kill 

 them. Place the uncorked 

 ends of the U -tubes in 

 the test-tubes. The py- 

 rogallic solution will, in a 

 short time, rise in the 

 U-tube about one-fifth of 

 its length, through the 

 absorption of the oxy- 



FlG. 18. Apparatus for study of respiration 

 in germinating seeds. The tubes contain, 

 respectively, water, solution of caustic 

 potash, concentrated mixture of caustic 

 potash and pyrogallic acid. X 4. 



gen ; the seeds will not germinate, or, if at all, extremely little. 

 In the potash tube the liquid will rise to the same height, but 

 more slowly, and the seeds will germinate and grow considera- 

 bly. In the water tube the liquid will scarcely rise at all, though 

 the seeds will grow as in the preceding. Of course, in the sec- 

 ond tube, in the respiration accompanying their growth, the 

 seeds absorb the oxygen and give off carbon dioxide, which 

 is absorbed by the potash, and the latter rises to occupy the 



