THE CHARACTERISTICS OF LIVING THINGS 19 



and others which move leaves and other parts, there are in 

 plants many movements which can be detected only with the 

 aid of a good microscope. 



(D) Examine any plants available which show any of the move- 

 ments mentioned above. Many will be found at greenhouses. Leaf- 

 lets of the Elodea (an aquatic plant) are excellent for the movements 

 visible with the microscope. A piece of an oyster's gill will show 

 microscopic movement going on in animals (see 338). 



25. Plants require food'ii they are to 

 continue to live and grow. It is a well- 

 known fact that ordinary garden plants 

 will not grow well unless there is a 

 supply of fertilizer (one kind of crude 

 plant food) in the soil. It will be shown, 



in a later lesson, that green plants do Fl _ G - 2 - Lea ' [ 



' & j i fly-trap adapted for 



not grow well if kept long in darkness, catching insects, 

 because light enables them to make use (From Strasburger.) 

 of certain food materials. 



26. Plants breathe. In no plant is it possible to see 

 breathing movements, as in animals; but it is possible to 

 prove by the lime-water test that changes are produced in 

 the air by breathing of plants. 



(D) Take about twenty pea or corn seedlings (directions for 

 raising such seedlings are given in first lesson on germination of 

 bean, 81). Place in a loose bag of netting, such as was used for the 

 experiment with the frog ( 20). Then lower the seedlings into 

 a wide-mouthed jar filled with fresh air, and after 24 to 48 hours lift 

 out the seedlings and test the air by pouring in some lime-water. 

 A second jar without seedlings, but otherwise treated in exactly the 

 same way, should be kept for comparison (control experiment). 

 Take all the care suggested for the corresponding experiment with 

 the frog. Compare results with that experiment. The breathing 

 in the plants is so much slower than in animals that the same amount 

 of change in the lime-water is not to be expected. 



A potted plant, such as a geranium or a begonia, if placed under a 

 bell-jar beside a small dish filled with lime-water, will give the same 

 proof that the plant causes changes in air, just as animals do when 

 breathing. 



