3O Gardening 



supply of the minerals that it needs. These minerals are 

 dissolved in only small amounts in the soil water, and to 

 get enough of them a plant must take in large quantities 

 of water. The greater part of this is given off by the 

 leaves into the air in the form of water vapor. This 

 evaporation of water from the leaves is called transpira- 

 tion. 



The advantage of transpiration to the plant is that 

 it allows large amounts of water containing weak solu- 

 tions of minerals to be taken in by the roots, and when 

 the water is evaporated the minerals are left in the plant. 

 The minerals in water remain in a kettle when the water 

 is boiled away; similarly, the minerals remain in the 

 leaves when the water is given off into the air. 



But in dry weather, transpiration is at times a disad- 

 vantage to a plant. Sometimes the roots do not absorb 

 water as fast as it evaporates from the leaves, and so 

 the plant wilts. One of the chief tasks of the gardener 

 is to provide enough water for the needs of his plants ; 

 for in hot, dry weather plants are often injured because 

 the water is lost too rapidly from the leaves. 



The stem and its work. The stem supports the leaves 

 so that they will be distributed widely in the air .and can 

 receive much sunlight. It also carries the sap between 

 the roots and the leaves. The water and minerals that 

 are taken in by the roots as raw materials pass upward 

 through the stems to the leaves, where they are manu- 

 factured into food for the plant. This food is then 

 carried downward through the stem to the roots or to 

 any growing and working part of the plant. By hold- 

 ing up great numbers of leaves to the light, the stem 



