THE WORKING PLANT 



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planted bush, the work of food getting begins, the food supply 

 is increased, and the new plant revives and renews its growth. 

 How the root hairs feed. When we examine a root hair, 

 we find that it contains no visible pores through which water 

 can enter. We know that water does pass through the root 

 hairs, however, and a simple experi- 

 ment will show how it enters. Fasten 

 a soaked membrane, such as the 

 bladder of a fish, or the skin of sau- 

 sage, to the broad end of a thistle tube, 

 and fill the bulb with sirup. Support 

 the thistle tube in a jar of water in 

 such a way that the sirup within the 

 thistle tube is on a level with the water 

 tn the jar. (See Fig. 307.) In a few 

 hours the sirup in the thistle tube 

 rises above the level of the water out- 

 side. Water from the jar has passed 

 through the membrane and has made 

 a place for itself in the narrow tube. 

 If the experiment is left standing for 

 a long time, a little sirup may pass 

 through the membrane into the water, 

 but the amount is extremely small. 

 The passage of liquids from one side 

 of a membrane to the other is called FlG - 307. An experiment to 



illustrate osmosis. 

 osmosis. 



Root hairs contain sap, a liquid which is denser than the soil 

 water which surrounds them. The water passes by osmosis 

 through the delicate walls of the root hairs and becomes a part 

 of the plant. 



The working plant. The nourishment stored in the seed 

 by the parent plant is just sufficient to give the seedling a start 



