70 THE BEGINNER'S GARDEN BOOK 



is always denser at the top. Then the thinner solution is 

 always pressing upward, and the leaves are easily supplied. 



If the soil water were very dense, that is, if we should 

 water our plant with the salt solution, which is heavier than 

 sap, the circulation would of course turn the other way. The 

 sap would pass downward instead of upward, and the plant 

 would die. 



We have not yet proved, however, that soil water has any- 

 thing in solution. This can be shown by an experiment 

 with which we must take some pains. Take some clean 

 sand, enough to fill two flower pots, and heat it over a hot 

 fire until you have burned everything in it that can burn. 

 Fill the pots with this sand when cool, and in them set two 

 plants of equal size : seedlings of corn or beans will do. 

 Now get a few pailfuls of rain water, or melted snow. 

 Neither of these has been in the soil. Keep part of it in one 

 can, and put the rest in another can in which you will stir a 

 few quarts of the richest loam that you can find. Now keep 

 the two plants watered differently, one with the rain water, 

 the other with the water in which the loam has been mixed. 

 In a few weeks the second plant should be very much stronger 

 than the other. This can only be because the soil water has 

 brought more food than the rain water. 



Well water, which has passed through the earth, has also 

 dissolved something from the soil. Plants will grow in it 

 better than in rain water. We can try this by fastening into 

 slit pieces of wood or cork, seedlings of plants such as tomato 

 or lettuce, which have no large cotyledons. Float some of 

 these in well water, others in rain water, and see which grow 

 the faster. 



So much for the plant's need of water. But one more 

 thing we need to understand. If we water a plant so freely 

 that the earth is "soaking full," so that its top is always 



