62 SCHOOL AND HOME GARDENING 



The movement of liquid in one case is opposite in direction 

 from the other. In the first case, the water moves into the 

 plant and keeps it fresh because the cell sap is denser than 

 the water. In the second case the cell sap is weaker than the 

 sugar syrup and the movement of liquid is toward the syrup. 

 This causes the wilting of the cells of the plant. 



When plants are in soil where the soil water is denser than 

 the cell sap, they will wilt instead of grow. This may be the 

 case when too much fertilizer is placed close to very young 

 plants. 



7. Sunlight Needed for Growth. — In a window box of plants, 

 place a tin can over a few plants in such a way as to entirely exclude 

 the light from them. After a few days, notice that the green color 

 of the leaves is mostly gone. In time, the plants will be killed. 



Gardeners place celery in trenches, dark cellars, or similar 

 places, to exclude the light. This causes the color to leave 

 the stems and makes the product much more salable. 



Plants require light on their leaves for their best growth. 

 If a box is inverted over green grass on a lawn for some time 

 it will kill the grass. If weeds in the garden are thoroughly 

 covered with soil by the use of a cultivator, they will probably 

 be killed. Mulches of straw about strawberries or other garden 

 plants help to prevent the growth of weeds. 



8. Leaves and Light. — In the window box of growing plants, 

 observe the leaves with their broad surfaces turned toward the light. 

 If possible, turn the box around and note the time required for the 

 leaves to change their position and turn again toward the light. 



Leaves of plants growing in a crowded condition, as in a 

 closely planted garden or in a forest of trees, seek the light. 

 The lower branches of an elm tree, for example, bend down, 

 the middle branches are more nearly straight out, and the 

 upper branches extend upward. This arrangement of the 

 leaves and branches of the tree gives the tree the greatest 

 amount of light exposure. Xote the effect of light on sprout- 

 ing tubers as shovm in figure 40. 



