THE LIVING SUBSTANCE OF PLANTS. 



entirely fill the root hair. But here and there are seen strands of this sub- 

 stance which cross the thread leaving clear spaces between. Or the clear 

 spaces appear as rounded vacuoles of different sizes, 

 or the vacuoles are more or less elongated. These 

 clear spaces in the root hair are occupied by a watery 

 substance known as the cell sap. 



Demonstration 5. 



37. Test for protoplasm. Draw off the water from 

 under the cover glass by the use of filter paper, and 

 at the same time add some of the solution of iodine 

 with a medicine dropper. Observe that the proto- 

 plasm is stained a yellowish-brown color. This is 

 the reaction of protoplasm in the presence of iodine. 



Exercise 1 O. 



38. Study root hairs of seedlings. Some of the 

 seedlings prepared in demonstration 2 can be used 

 by the members of the class for a study of the gross 

 appearance of the root hairs. 



Make a sketch of the seedling showing what por- 

 tion of the root is covered by the root hairs. Why 

 are not the root tips covered with the root hairs? 

 Why are the root hairs absent from the older portions 

 of the roots ? As to strength and firmness how do 

 the root hairs and roots compare ? Test this by 

 handling. 



Immerse the portion of the root covered by the 

 root hairs for a few moments in a solution of iodine. 

 Do they take the stain ? Will the stain all wash out 

 in water when immersed for a few moments ? 



Take a fresh seedling with uninjured root hairs 

 and immerse the root for a few moments in a 1% 

 aqueous solution of eosin. Rinse in water. Do the root hairs hold the 

 stain ? Immerse the root for a few moments in strong alcohol, or in 2% 

 formalin, and then immerse the root hairs in eosin. Rinse in water. Do the 

 root hairs hold the stain now ? Why ? 



Write out a complete account of your experiments and observations. 



Fig. 7. 



Root hairs of corn be- 

 fore and after treatment 

 with 5% salt solution. 



