APPENDIX I. 73 
(b) The Path of the Downward Movement of Nutriment. 
Take two leafy willow twigs of equal size, and at equal 
distances from cut ends remove rings of bark of the same size. 
Place each in a vessel of water, so that in one the water level is 
below the girdle and in the other it is above the girdle. After 
some days observe the difference in root formation, and explain 
the larger roots above the girdle in the second specimen. 
EXPERIMENT 12. TO SHOW RESPIRATION. 
(a) For oxygen inhalation consult Experiment 3. 
(6) For carbon dioxide exhalation in — 
(1) Algz and green plants in darkness. 
Place vigorously growing algee or oats in jars in the evening, 
and tightly stopper the bottles. In the morning plunge a 
lighted taper in each jar. It is extinguished. Why? 
(2) Growing yeast. 
In a jar containing vigorously growing yeast, note the evolu- 
tion of a gas; close the jar and allow it to collect, and test by 
a lighted taper. Or pass this gas through lime water. What 
is the explanation ? 
(3) Growing seeds. 
Take a number of growing seeds and place them in a bottle 
and close with a rubber stopper. After some hours test with 
taper or lime water and observe results. 
(4) Growing roots. 
Grow some seedlings in earth on a marble slab. After a 
couple of weeks, observe the etching of the marble where the 
roots came in contact with it. Carbonic acid has been thrown 
off by the roots and has dissolved portions of the marble. 
