LESSONS WITH PLANTS 



339 



ditches, may be shown with the compound miscroscope. 

 These httle uniceHular plants ha\-e the power of locomotion. 

 On moist earth in ditches there is often a coating of bluish- 

 green alg;ie, the Oscillatoria, which also have some power 

 of movement. There arc 

 spore-cells set free by 

 man}- plants that swim 

 acti\elv about, and are 

 reproductive devices. 



Though the larger 

 plants may not move 

 about, yet they can move 

 their various parts. A 

 few observations on 

 growing plants will show 

 them to be thoroughly 

 alive and active. 



In a glass germinator 

 ("see p. 300) notice how 

 the roots of seedlings 

 crrow do\A'n. Invert the 



o 



germinator. Note that 



in a day or so the roots 



have turned and now grow downward again. They seem to 



know enough to grow down. 



Note also how a rootlet bends away from and around an 

 obstruction, such as a pebble placed in its course. The 

 root is sensitive to touch and responds by a curvature. 



Plant a sunflower or other seedling in the drain hole of a 

 small flowerpot full of earth and hang it up somewhere. Note 

 that soon the stem curves upward. The same may be shown 



Fig. 136. 



Squash Seedling Laid on its Side has 

 Straightened up Again. 



