The Kinds of Work That Are Done by Plants 81 



out the complications introduced by photosynthesis (e. g., ger- 

 minating seeds, such as Oats), then close the bottle air-tight by 

 means of the stoppers and clamp provided for the purpose, and 

 stand it for some hours in a warm 

 and dark place where growth can 

 take place. Obviously, any carbon 

 dioxide released by the seeds must 

 collect in the bottle, where its pres- 

 ence may be detected by its well- 

 known property of turning clear lime- 

 water milky. If, accordingly, clear 

 limewater is poured into the tall vessel 

 into which the delivery tube leads, 

 the clamp is loosened, and water is 

 poured down the thistle tube, then 

 the gas will be forced from the bottle 

 and sent bubbling up through the 

 limewater. The result is always de- 

 cisive. The limewater turns white- 

 milky proving the presence of car- 

 bon dioxide hi abundance. And if 

 a bright person should here rise to 

 remark that the carbon dioxide al- 

 ways present in air is sufficient to ex- FIG. 27. A Respiroscope, or ar- 



... . rangement for demonstrating that 



plain the result, it IS easy tO prove it plants respire. Its operation is 



is not; for, if an equal quantity of air explained in the text ' 

 be forced from an empty bottle through limewater no milkiness 

 appears. Arid if, in the bottle, we place buds, or roots, or color- 

 less plants like Mushrooms, or even green leaves (in the dark), the 

 result is always the same. Furthermore, it is also the same whether 

 the working parts are kept in the light or the dark, and it is still 

 the same, as the reader may be confounded to learn, even with 

 green leaves when kept in the light, though here the process is 

 obscured by the absorption of that gas in photosynthesis, as can 



