FUNCTION AND STRUCTURE OF ROOTS 



121 



at the rooting point. In the leaf rosettes of herbs growing 

 flat on the ground or in the 

 crevices of walls and pavements, 

 the strong depression observable 

 at the center is due to root pull. 



166. Roots absorb Moisture. 

 Fill two pots with damp earth, 

 put a healthy plant in one and set 

 them side by side in the shade. 

 After a few days examine by dig- 

 ging into the soil with a fork and 

 see in which pot it has dried most. 



Where has the moisture 

 how did it get out ? 



gone 



167. Roots shun the Light. 

 Cover the top of a glass of water 



with thin netting, lay On it Sprout- 257. Raspberry stolon showing 



ing mustard or other convenient 



seed. Allow the roots to pass through the netting into 

 the water, noting the position of root and stem. Envelop 

 the sides of the glass in heavy wrapping paper, admitting 

 a little ray of light through a slit in one side, and after a 

 few days again observe the relative position of the two 

 organs. How is each affected by the light ? 



168. Roots seek Air. Remove a plant from a porous 

 earthenware pot in which it has been growing for some 

 time ; the roots will be found spread out in contact with 

 the walls of the pot instead of embedded in the soil at the 

 center. Why is this ? 



169. Roots seek Water. Stretch some coarse netting 

 covered with moist batting over the top of an empty 

 tumbler. Lay upon it some seedlings, as in Section 167, 

 allowing the roots to pass through the meshes of the net- 

 ting. (A piece of cardboard with holes in it will answer.) 

 Keep the batting moist, but take care not to let any of the 

 water run into the vessel. Observe the position of the roots 



