no 



BOTANY. 



length ? Which plants have the larger leaves ? What influence does light 

 have on the development of leaves ? What is the difference in color of the 

 plants ? What is the cause of this ? Which lot of plants have the firmer 

 tissues ? What is the cause of the difference in the firmness of the tissues ? 

 Sketch a plant grown in the dark ; sketch one to the same scale grown in 

 the light. 



Exercise 42. 



192. Influence of light on the direction of growth. — Take potted seed- 

 lings and place them near a window so that they will. have a one-sided illu- 

 mination. Or place 

 them in a box which 

 has a small opening 

 at one side. After a 

 day or two observe 

 the position of the 

 seedlings. Does light 

 have an influence on 

 the direction of 

 growth ? What is the 

 direction with refer- 

 ence to the source of 

 light ? Sketch one 

 of the plants, and 

 indicate on the sheet 

 the direction of the 



fl'lt Fig 86 ' 



* * ' Radish seedlings, grown in the 



193. Influence Of dark, long, slender, not green. 



light on the position of leaves. — Take potted 

 plants with a number of leaves, and place them 

 near a window for several days or a week. Ob- 

 serve the position of the leaves at the beginning Fig. 87. 



of the experiment, and after a week's time. What , R ?. di . sh seedlings grown in 



the light, shorter, stouter, and 

 is the position of the leaves with reference to the green in color. Growth re- 

 source of light ? Can you tell why the leaves take tar e y lg "■• 

 this position ? 



194. Retarding influence of light on growth. — We have 

 only to return to the experiments performed in growing plants 

 in the dark to see one of the influences which light exerts on 

 plants. The plants grown in the dark were longer and more 



