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. 

 h. Ascertain how they are connected with the body 



of the root. . Draw. 

 0. 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. Suspend seedlings in a wide-mouthed 

 jar, the air within which is kept saturated with watery 

 vapor. With a camel's-hair brush and India ink make a 

 series of marks at intervals of a millimeter, beginning at 

 the apex of the root. Ascertain by subsequent observa- 

 tions, about a day apart, where elongation has taken 

 place. 



V. Determine the direction naturally taken by roots. 



