THE ROOT 17 



kinds of soil, and its dependence on the amount of 

 clay or of organic matter present. 



The water is retained between and round the par- 

 ticles, and the smaller the particles, the greater the 

 sum total of their surfaces, and the greater the amount 

 of water retained by the soil. 



3. Let us now consider the root and its functions. 



In the first place a plant is fixed in the ground by 

 its roots. Dig up any plant, or better, take one that 

 is growing in a pot. Carefully remove all the soil, by 

 washing in water, so as not to break more of the 

 rootlets than you can help. Dry them and measure 

 each separate root and rootlet. Add all the measure- 

 ments together and you will find that the total length of 

 the whole underground portion is immense ; it may be 

 even a thousand times the height of the shoot. This 

 means that the soil under a well-grown plant is 

 pierced through and through in all directions by the 

 roots, so that there is not a cubic inch of earth, 

 hardly even a piece the size of a gram seed, but has a 

 rootlet passing through it. 



Now put some seeds of Maize or of Mustard on a 

 piece of red blotting-paper, cover them over, and keep 

 the paper damp for three days. At the end of that 

 time roots will have grown out, and round each will 

 appear a glistening white border which, looked at 

 through a magnifying glass, is seen to consist of numer- 

 ous very thin threads or hairs. These are really 

 extremely fine tubes, and are termed root-hairs. 

 They grow only on the youngest parts, i.e. towards 

 the ends of the rootlets, and die off after a while. 

 As the roots make their way through the earth, the 

 2 



