X. 



ROOTS 



Plants, as we have seen, need a constant supply of 

 water for transpiration and for growth. They cannot, 

 as a general rule, take this in by their leaves, and 

 therefore must take it in by their roots ; and without 

 water the roots cannot take up and supply to stem, 

 branches, leaves, flowers, and fruit that mineral matter 

 without which the plant cannot exist. 



Before examining the way in which the roots perform 

 their work of supplying all parts of the plant with 

 liquid food, we must briefly consider where the water 

 comes from. 



For if, as has been said, the ordinary rainfall in 

 England for the whole month of July is about 300 

 tons, and if an acre of pasture-grass transpires more 

 than 3,000 tons in the same tfme, it is quite evident 

 that the demand far exceeds the supply from the 

 clouds. Moreover, the grass does not get even the 

 full benefit of that which does fall, for a very large 

 proportion is either at once evaporated from the 

 soil, or is drained away into ponds, lakes, streams, or 

 rivers. 



Of the rain which falls in England between April i 



