12 THE NATURE AND WORK OF PLANTS 



This last fact is due to the action of the current of 

 water which constantly travels upward through the 

 stem into the leaves where it evaporates and passes 

 off into the air, leaving behind all the mineral sub- 

 stance brought up from the soil. 



9. Leaves shrink in drying. — During the drying 

 process the loss of water brings the particles of 

 which the plant is composed closer together, and it 

 shrinks in size. This may be best seen in leaves. 

 Place a leaf of sunflower or some fresh rapidly grow- 

 ing leaf on a sheet of paper, and trace its outline 

 with a pencil. Now put it between two sheets of 

 blotting paper on which is placed a weight of ten 

 pounds. Eeplace the blotting paper twice a day for 

 three or four days. Place the dried leaf over the 

 original tracing, and make a second drawing of its 

 outline. The leaf has decreased in length and width. 

 Measure the amount. 



10. Mineral coatings. — During the life of the 

 plant the mineral substances in it are usually dis- 

 solved in water and are not visible. In some in- 

 stances, however, these minerals take the form of 

 small crystals which can be seen with the micro- 

 scope. In still other cases the mineral is deposited 



