Roots 



105 



the shallow ones may; and unless this water be buried 

 under some bed through which it cannot pass, it will con- 

 tinue to rise to the surface. 



The water which plants need, therefore, for growth, 

 and to supply the small loss by evaporation and the large 

 loss by transpiration, comes to them from rain and dew; 

 it is also very largely absorbed from the air by the soil; 

 and the large stores accumulated in the ground are also 

 drawn upwards as they are needed — chiefly, of course, 

 during the spring and summer. In autumn, when growth 

 ceases, transpiration is less; in winter, when the trees are 

 bare, there is next to none, so that they have little need 

 of water. In spring and summer, on the other hand, they 

 need much, and receive it, in part, from the accumulated 

 stores of the other months. 



All the water which plants transpire — in many cases a 

 very large quantity, as we have seen — is taken up by their 

 roots, and their roots alone. And these roots we must 

 now look at a little more closely. 



A root is a very wonderful organ, much more wonder- 

 ful than a passing glance would lead one to suppose. 

 And, indeed, the most important parts cannot even be 

 seen without careful examination. 



The root serves two purposes: it keeps the plant in 

 one place, enabling it to stand against the wind; and it 

 collects from the soil food and water which the plant can 

 obtain in no other way, and without which it can neither 

 grow nor exist. 



Some plants have a single fleshy root, like that of a 

 carrot, which descends straight into the earth, and has no 

 branches, but only a few fibers growing from it. A car- 

 rot needs a good pull to uproot it; but an onion is easily 



