26 NATURE TEACHING 



within a few hours the end of the root bends so that 

 once again the tip is directed vertically downwards. A 

 simple experiment such as this is sufficient to show that 

 plants are not mere passive living things, but can 

 control the movements of their parts almost as if they 

 possessed senses similar to those of animals. 



Roots increase in length by the addition of new 

 material at their ends ; the older parts may grow in 

 thickness, but they do not increase in length. Indeed, 

 a moment's consideration will show that this must 

 necessarily be the case, for if roots were to grow in 

 length anywhere but at their ends they would tear off 

 their branches, which are firmly embedded in the soil. 



Uses of Roots. 



Roots have several uses : they fix the plant firmly in 

 the soil, they absorb water together with the nutriment 

 which plants derive from the soil dissolved in it. This 

 absorption of water is only effected by the younger 

 portions of the roots being .practically confined to the 

 root-hairs. The region, therefore, which bears the 

 root-hairs is the absorbing region, and this fact explains 

 the importance of the young roots and why plants 

 suffer if these are unduly disturbed or injured. The 

 older parts of the root have no power of themselves to 

 take up water and plant food. They are of use as 

 mechanical supports, and also as the means whereby 

 the water taken up by the absorbing region is passed 

 on to the stem and leaves above ground. 



Roots frequently act as storehouses of plant food, 

 particularly in the case of biennial plants. Biennials 



