34 AGRICULTURE 



in a horizontal direction, should the soil at 

 any point become drier than adjacent soil 

 on the same level. When, for instance, a 

 plant is feeding, that is to say, when it is 

 taking in mineral food dissolved in water, 

 its root hairs are draining the soil of moisture 

 in their immediate neighbourhood. Had the 

 soil no power to bring fresh supplies of 

 water into contact with the root hairs, the 

 latter must cease to feed directly they have 

 abstracted the moisture from the soil in 

 their immediate vicinity. But no sooner is 

 the moisture withdrawn from such soil than 

 equilibrium is upset, and from all directions 

 from below, from the side, from above the 

 small mass of soil, which has been drained 

 in the way indicated, has the power of 

 attracting water, so that there is a constant 

 movement of moisture towards the tips of 

 the roots, namely, the parts of the plant 

 where water is most required. This water 

 carries with it the potash, phosphates, 

 nitrates, and other plant food required by 

 the crop, and although the solution is a very 

 weak one the aggregate amount of mineral 

 matter and nitrates that passes into an 

 average crop in a growing season may 

 amount to several hundred pounds per acre. 

 It is this food that nourishes the cells of the 



