FEBBUARY 159 



In addition to the observation of the growing seeds, 

 such experiments shoukl be performed as will demon 

 strate clearly to the children that these seeds are alive ; 

 that like the animals, they not only grow, but that they 

 also breathe and eat. 



Facts : 



Plants, like animals, breathe out carbon dioxide. This 

 they do continually, but owing to the oxygen given out 

 in the assimilation of food, a life process which takes 

 place only in the light, respiration is most easily shown 

 with plants that are kept in the dark. 



Plants take in nourishment osmotically through their 

 roots. This food consists of water and substances dis- 

 solved in it. They are able, however, b}^ means of an 

 acid secretion, to act upon carbonate of lime, which is 

 then available for food. 



Method : 



It is first necessary to show what breath really is. 

 Let the children breathe against their ha:ids, against 

 a cold surface, such as the board, into a little clear lime 

 water through a straw or glass tube. 



Why is the breath warm ? What does it contain ? 

 What effect has it on the lime water? 



The turbidity of the lime water is due to the fact that 

 the carbon dioxide of the breath precipitates lime car- 

 bonate, a white solid, and therefore easily seen in the 

 water. 



These experiments establish the fact that we breathe 

 out carbon dioxide and water vapor. This is true of all 

 qnimals. Is it true of plants ? 



