36 PHILIPPINE AGRICULTURE 



fresh and in the proper form. If the vacuoles lose much 

 water, the plant wilts. Wilted plants cannot grow. 



Mineral Food. Plants need water for the mineral food 

 dissolved in it. Boil water from a well in a kettle for a 

 long time, and you will find a lining or sediment in the 

 kettle ; this is made of salts which were in the water, and 

 were left behind when the water evaporated. Water 

 evaporates from the leaves of plants, and the substances 

 dissolved in the water are left behind. 



Transpiration. Evaporation from living plants is called 

 transpiration. The water transpired by plants is many 

 times as much as the water needed for building material. 

 Except for their transpiration, plants would be practically 

 unable to get their mineral food, however much of it 

 there might be in the ground. 



Transpiration takes place almost entirely from the 

 leaves. If it is too active, the plants wilt, and wilted 

 plants can neither grow nor make their food. If wilted 

 plants continue to lose water too rapidly, they die. But 

 so long as growing plants are able to get water as rapidly 

 as they lose it, and so prevent wilting, the most rapid 

 transpiration is the best ; because the more rapid is the 

 transpiration, the more mineral food is obtained. Sun- 

 light, wind, dry air, and warmth help transpiration. On 

 the other hand, darkness, moist air, still air, and cold 

 hinder transpiration. 



The Transpiration Stream. The water transpired by the 

 green, soft parts of the leaves reaches them through the 

 veins and ribs. It comes to these through the petiole 



