30 STUDY OF COMMON PLANTS. 



(The roots of wheat or oat seedlings are excellent 

 for this .purpose.) Mount in water, taking care 

 not to injure the delicate tissue by undue press- 

 ure. Examine under a high power of the com- 

 pound microscope. 



a. Observe the structure of the root-hairs. 



b. Ascertain how they are connected with the body 



of the root. Draw. 



c. Run iodine solution under the cover glass, and 



watch the effect. What do you- infer as to the 

 permeability of the cell membrane and the 

 capacity of the cell contents for absorption ? 

 3. Pull up a specimen that has grown in clean sand. 

 Shake off as many of the adherent particles as 

 possible. Examine under a good lens. It will be 

 seen that many grains of sand still remain attached. 

 Ascertain whether this is due in any way to the 

 presence of root-hairs. 



III. Cut off the tips of some of the fine roots of wheat 

 or oats grown under a bell-jar. Mount in water, and 

 examine with the compound microscope. Select a good 

 specimen, and draw the end carefully so as to show the 

 root-cap. 



IV. Determine in what part of the root increase in 

 length takes place.. Use for this purpose roots of Indian 

 corn, peas, or sunflower, growing on moist blotting paper 

 under a bell-jar. With a camel's-hair brush and India ink 

 make a series of marks at intervals of a millimeter, begin- 

 ning at the apex of the root. Replace the bell-jar, and as- 

 certain by subsequent observations, about a day apart, 

 where elongation has taken place. 



V. Determine the direction naturally taken by roots. 



