PLANTS NEED WATER 105 



''""should be kept clean and open by frequent baths which 

 Bought to be taken daily, if possible. 



Dirt cannot be removed completely without the use 

 "of soap. ' There are two kinds of soap laundry soap and 

 " toilet soap. Soap which is suitable for washing clothes 



and for general housecleaning is usually unfit to be used 

 "on the skm. ' On the other hand, toilet soap, which is 



intended for tender skin, would have little cleaning 

 ;; power if used "on clothes. See Section 77. 



-40. Plants Need Water. 



We all know" that plants need water, for if we forget 



"to water them they quickly wilt, and, if they go too long 



without water they die. If the plants have only wilted 



they soon take up the water and become stiff and vigor- 



" ous again. In the next section we will learn the reason 



'for this change. The amount of water which plants 



"need is very great. The water is carried away from the 



leaves by evaporationjust as it is -carried from wet clothes 



"which are hung 'to dry. When we think of the very 



large surface of the leaves of a tree we wi 1 ! realize that 



the amount of water which can be given off is enormous. 



We call the giving off of water from the leaves of a 



plant transpiration. Transpiration ^takes place only on 



' "' the under si'de of ' leaves. 



Seeds will not begin to open unless' they are supplied 



with water. Then they swell' Trn'fil they 'burst, and the 



"young plant comes forth. The ^amotint'th'at'seeds swell 



'is always a surprise, as you know 'if you 'have ever "put 



beans to soak'." 



