THE WORK OF ROOTS AND STEMS 69 



It is very largely through these hairs that the roots 

 take in food from the soil. All the young soft tips 

 drink in moisture, but it is the tiny hairs which do 

 most of the work. 



A great deal of food is needed by the growing plant, 

 and especially a great deal of water. You would hardly 

 believe what a quantity of the latter has to be taken in. 

 Those plants which live entirely in water have really 

 very little that is solid in their make; and even with 

 land-plants at least half of their substance is in most 

 cases water, and often as much as three-quarters. So 

 we can easily imagine what supplies of it a plant must 

 drink to keep itself going. 



In fact, a plant can in its way be just as hungry 

 and thirsty as a man; and if food and water fail or 

 become scanty it droops and gets limp and weak, just 

 as a human being would do. This drooping of leaves 

 and stem is often called " wilting." 



Sometimes only a few root-hairs are to be found. 

 Sometimes such numbers of them are crowded together, 

 round about the root -tip, that it seems to be clothed 

 in a kind of thick velvet. Their business is to suck up 

 water, and at the same time they receive whatever 

 of solid substances may be dissolved and floating in the 

 water. 



Root-hairs are really cells on the outside of the 

 root-tip, and it is when need arises that some of the 

 cells lengthen into hairs. Not only do they become 

 long and thin, but also they gain a curious power to 

 suck, so that they can draw away water and salts 

 clinging to specks of soil : clinging, indeed, so fast that 

 force is often needed before they can be dislodged. 



