USE OF WATER IN PLANTS. 73 



I BE OF WATER IN PLANTS. 



1. Every-day experience shows us that it' 

 a leafy shoot is picked it soon becomes liinp and 

 then withers, but that if we place it in water it 

 remains fresh and stiff for a longer time. Fur- 

 ther, we know that the shoot which has com- 

 menced to wither can often be made fresh again 

 by placing the cut end of its stalk in water. 

 Similarly, plants growing in the ground droop 

 and may die if they are deprived of water for 

 a long time. They soon revive if water is 

 poured on the soil so as to penetrate down to 

 their roots. From these various facts it is 

 clear that the withering and limpness of the 

 leaves is due to the fact that they give oft 

 water, and that more can be supplied to them 

 either by putting the cut end of the stalk in 

 water, or, as happens in nature, by water being 

 taken up by the roots and passed on through 

 the stem to the leaves. 



'2. This loss of water by the leaves is 

 known as transpiration, and is of great impor- 

 tance to the plant, because as water is given on" 

 from the leaves more is steadily drawn up 

 through the stem to take its place. When a 

 plant is growing and has plenty of water at 

 its roots water is taken up almost as quickly 

 as it is given off and the whole plant remain- 



