USES OF ROOTS. 29 



4. Roots usually grow down into the 

 soil, throwing out numerous branches and 

 permeating the soil with a network of fine 

 rootlets each provided with root-hairs and 

 terminating in a root-cap. Roots increase in 

 length by the addition of new material at their 

 ends ; the older parts may increase in thick- 

 ness 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 oft' their branches which are 

 firmly embedded in the soil. 



USES OF ROOTS. 



1. 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, there- 

 fore, which bears the root- hairs is the absorb- 

 ing 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 



