190 THE NATURE AND WORK OF PLANTS 



drawn from the cells, and the plant will become as 

 limp as if it were wilted in the sun. Cut off the 

 plump, rapidly growing shoots of any soft-bodied 

 plant and lay them in a deep dish which contains 

 water saturated with sugar or salt. Examine after 

 a few hours. The shoots will be found limp and 

 weak, and bend over when you attempt to hold 

 them upright by the basal parts of the stems. 



229. Outward work accomplished by physical 

 attraction. When water is attracted into a cell 

 the cell expands with a force which may be equal 

 to twenty times the pressure of the atmosphere. 

 The expansion of the cells of a root will split 

 apart rocks and perform similar work. This may 

 be demonstrated as follows: Fill a narrow-necked 

 bottle of a capacity of four to eight ounces with 

 dried peas. Next pour in as much water as the 

 bottle will hold, and then, without admitting air, 

 invert the bottle, and set the mouth in a dish of 

 water. Examine a day or two later. The cells of 

 the seeds will have taken in so much water under 

 the attractive power of the substances which they 

 contain that they have expanded and burst the 

 walls of the bottle. 



