EXERCISE VIII. 

 THE FUNCTION OF ROOT-HAIRS. 



Supplies for a Laboratory Section of Twelve. Twenty-four pie tins; forty-eight pieces of blotting paper; radish 

 seeds; tnree magnifiers; one razor; one compound microscope; molasses solution; one parchment tube previously 

 soaked; one one-hole rubber stopper to fit parchment tube; one glass tube about 8" long; one wide mouth bottle j 

 twelve potatoes: salt solution; twenty-four evaporating dishes; one egg; one glass tube about 6" long; sealing wax; 

 one small beaker. 



Part A. Root-Hairs. 



Germinate a few radish seeds in a germinator* with just enough water to keep the 



seeds moist, but not wet. If the seeds become infected 

 with mould, it will be necessary to start the experiment 

 over again. When the roots have grown to a length of 

 H centimeters, examine them with a hand lens for the 

 presence of root-hairs, (a) Notice what part of the root 

 is covered with root-hairs, (b) Make a neat drawing of 

 the young radish plant (natural size) showing the distri- 

 bution of root-hairs along the root. 



2. With a very sharp razor, cut thin cross sections 

 of the root at such a place as will show the root-hairs 

 to the best advantage. Examine these sections under 

 thf compound microscope. Do the root-hairs appear to 

 be made up of a single cell or several cells? 



Part B. Osmosis. 



Fig. 4. Home-made seed tester; (a) 

 closed; (b) open. (Farmers' Bulletm, 382.) 



3. (Classroom experiment.) Fill a parchment tube 



with molasses solution. Into the mouth of the parchment 



tube fit a one-hole rubber stopper through which passes a 



small glass tube about eight inches in length. Suspend 



the tube in a bottle of water in such a position that the level of the molasses solution in the 



tube will correspond with the level of the water in the bottle. After a time observe any 



change in level. 



Notice that the liquid in the parchment tube contains more material in solution than the 

 water in the bottle. Furthermore, observe that the liquid containing very little material in 

 solution, passes into the parchment tube more rapidly than the liquid containing much material 

 in solution is able to pass outward. This unequal passage of liquids through the parchment 

 causes the rise of liquid within the small glass tube. This phenomenon is called osmosis. 



4. Place a few fresh slices of potato in a dish of water. Also place a few in a strong salt 

 solution, (a) After a few minutes observe any difference in the feeling of the slices of potato, 

 (b) The slices of potato are made up of cells largely filled with water and protoplasm. If 

 the ordinary amount of liquid present in the potato cells is decreased what effect will it have 

 upon the turgidity of the potato slices? (c) What evidence do you have that the liquid con- 

 tents of the potato cells contains more material in solution than ordinary well water? (d) 

 What evidence is there that the liquid contents of the potato cells contain less material in 

 solution than the strong salt solution? 



"Note: Two pie tins and four sheets of blotting paper are all that i» necessary to make a simple germinator. 



22 



