PLANT ROOTS 



369 



ROOTS SECURELY HOLDING THE TREE ERECT 



If the solution is too strong, as seen in Experiment 109, 

 the plant cannot use it. This is the reason many alkali 

 soils will not support 

 plants. The alkali 

 salts are so readily 

 soluble that the soil 

 water becomes a solu- 

 tion stronger than the 

 plants can use. 



Experiment 110. 



Place three or four 



thicknesses of colored 



blotting paper on the 



bottom of a beaker. 



Thoroughly wet the 



paper and scatter upon 



it several radish or other seeds. Cover the beaker with a piece of 



window glass and put in a warm place. Allow it to stand for 



several days, being sure to keep the blotting paper moist all the 



time. When the seeds have sprouted, examine the rootlets, with 

 a magnifying glass or low power microscope, for the 

 root hairs which look like fuzzy white threads. Touch 

 the root hairs with the point of a pencil. They can- 

 not, like the rest of the root, stand being disturbed. 

 On what part of the plant root do the root hairs grow? 

 As the blotting paper dries, what happens to the root 

 hairs? 



Plant roots are enabled particularly by the 

 little root hairs (Figure 108), which were ex- 

 amined in Experiment 110, to take the film of 

 FIGURE 108 water which surrounds the soil particles and carry 

 this water to the stem and, through it, to the 

 leaves. The water which the roots take from the soil is a 

 dilute solution containing the plant food substances. Not 



