THE LIVING SUBSTANCE OF PLANTS. 



17 



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

 :ance which cross the thread leaving clear spaces between. Or the clear 

 paces appear as rounded vacuoles of different sizes, 

 r the vacuoles are more or less elongated. These 

 lear spaces in the root hair are occupied by a watery 

 ibstance known as the cell sap. 



Demonstration 5. 



87. Test for protoplasm. — Draw off the water from 

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

 t the same time add some of the solution of iodine 

 ith a medicine dropper. Observe that the proto- 

 lasm is stained a yellowish-brown color. This is 

 le reaction of protoplasm in the presence of iodine. 



Exercise 1 O. 



38. Study root hairs of seedlings. — Some of the 

 :edlings prepared in demonstration 2 can be used 

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

 Dpearance of the root hairs. 



Make a sketch of the seedling showing what por- 

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

 e not the root tips covered with the root hairs? 

 fhy are the root hairs absent from the older portions 

 : the roots ? As to strength and firmness how do 

 ie root hairs and rcots compare ? Test this by 

 indling. 



Immerse the portion of the root covered by the 

 iot hairs for a few moments in a solution of iodine, 

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



water when immersed for a few moments ? 



Take a fresh seedling with uninjured root hairs 

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

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

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

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

 ot 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. 



