CHAPTER XIV. 

 RESPIRATION. 



185. Respiration occurs in all parts of plants. The 



leaves are also organs for respiration, but respiration takes place 

 in all living, active parts of plants. The subject will here be 

 treated with reference to plants in general. 



186. How seedlings breathe. Plants breathe just as truly 

 as animals do, though they do not have lungs. Breathing, in 

 animals as in plants, is usually accompanied by the entrance of a 

 gas, oxygen, into the body, and giving off, or excreting another 

 kind of gas, carbon dioxide. That germinating seeds give off 

 carbon dioxide can be shown in th.e following way: A quart of 

 peas which have been soaked in water for twelve or fifteen hours, 

 is placed, without any water, in two fruit jars or two large wide- 

 mouthed bottles, which are then closed tightly. Another jar or 

 bottle empty but closed tightly is kept as a check. In twenty- 

 four hours let us pour a small quantity of barium hydrate* into 

 the jar or bottle of peas, and close the bottle quickly again. A 

 white precipitate| is formed. If the bottle is opened again and 

 tipped so as to pour some of the gas into an open vessel with a 

 little barium hydrate, the white precipitate appears in the vessel 

 of baryta water. The gas is heavier than air and is easily poured 

 into the baryta water. If some of the barium hydrate is poured 

 into the empty bottle, no precipitate is formed or only a very 

 small quantity. 



Now in the other bottle of peas the lighted end of a splinter or 

 taper may be lowered. The flame is immediately extinguished 

 because of the presence of a suffocating gas, carbon dioxide. If 



* To make barium hydrate. Dissolve barium oxide in water. Filter and 

 keep in a tightly corked bottle. See footnote, (f) page 117. 

 f This is barium carbonate, BaCO 3 . 



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