CHAPTER XXXVI 



HOW PLANTS DO THEIR WORK 



We are now ready to consider plants in relation to 

 their environment and find out something about how they 

 do their work. One of the first questions that comes to 

 us is, how do roots of plants get the water with the other 

 raw material from the soil? 



Experiment. — Put some moist blotting paper or sand 

 in a dinner plate. Scatter over this at some distance apart 

 a number of radish or oat seeds. Turn another plate over 

 this to keep in the moisture and set in a warm place. 

 Water if necessary. At the same time plant a few seeds 

 in a pot or can of soil. After five or six days examine the 

 plants in the plate. What do you find on the roots? 

 Those delicate threadlike structures are root hairs. On 

 what part of the roots do you find them most abundant ? 

 Watch a plant for several days to see whether any of the 

 hairs wither and die and whether new ones continue to ap- 

 pear. Are there any at the very tip of the root? Can 

 you see any advantage in not having root hairs here? 

 Note what direction the tips take as they grow. What do 

 you think is the use of the root hairs ? If the little plants 

 were growing in the soil instead of on blotting paper the 

 root hairs would penetrate the spaces between the particles 

 of soil. Pull up one or two of the little plants that are 

 growing in the pot. Do any of the soil particles cling to the 



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