90 



Elementary Plant Physiology. 



Figf. 60. — Apparatus for test- 

 ing influence of light which has 

 passed through colored solu- 

 tions upon liberation of gases 

 by green plants. A, colored 

 fluid in outer cylinder ; /, inner 

 cylinder, containing plants and 

 water. After Oels. 



thrust the glowing wood into the 

 gas. If it glows more brightly, the 

 presence of oxygen is denoted. 



94. Portion of spectrum 

 by aid of which green plants 

 exhale oxygen. — Provide two 

 large cylinders about 25 cm. in 

 height, and two of about the same 

 height, but smaller diameter. Set 

 the smaller inside the larger ones, 

 and ballast with a weight of about 

 a kilogram. Fill the outer cylinder 

 around the smaller one, in one in- 

 stance, with a saturated solution of 

 potassium bichromate. Fill the 

 other with a solution made by add- 

 ing strong ammonium hydrate to a 

 saturated solution of copper sul- 

 phate as long as the foniiing pre- 



Fig. 61.— Preparations for estimating rate of liberation of gases by counting 

 number of bubbles. A sprig of an aquatic plant is fixed to a glass rod, with the 

 excised end of the stem uppermost. 



