416 TEXTBOOK OF BOTANY 



now point? If they have bent, in what part of each root did the 

 bending take place? 



7. Sprout seeds of radish, barley, and corn in sand or sawdust, 

 and when the roots are an inch or more long pull up some of the 

 plants. Note how the sand or sawdust sticks to the roots. What 

 holds it in place? What does this suggest as to the proper care 

 to be taken of the roots in transplanting young cabbage or tomato 

 plants ? 



8. Test such roots as those of beets, carrots, and sweet potatoes 

 for (a) starch, (6) sugar, and (c) proteins. 1 



9. Fasten a root of sweet potato or carrot in a bottle or tumbler 

 which contains water enough to cover the lower part of the root. 

 Observe the vigorous growth of the leaves which soon appear. 

 What is the source of food supply for the growth of the leaves ? 



CHAPTER XV 



1. Study with a hand lens a cross section of a basswood stem 

 several years old. Can you tell the age of the stem ? What differ- 

 ences do you find between spring and summer wood ? 



2. Study an underground stem of quack grass, iris, or Solomon's 

 seal. How old is it? How can you tell? What is the extent of 

 each year's growth ? 



3. Examine a potato tuber. What structures indicate that it is 

 really a stem ? Put a potato into a tumbler partly filled with water 

 and examine after a few days. What changes have taken place ? 



4. Cut a thin section across a potato tuber and hold it toward 

 .the light. Can you find regions that correspond to those found 

 in stems that you have previously studied? 



6. Cut off the lower end of a potato tuber and place the cut end 

 in a dish containing red ink. After some time cut across the tuber 



1 (a) Treatment with iodine, which turns starch blue, is the ordinary test for 

 starch, (b) Boil small portions of the root to be tested, and while the liquid is 

 still warm add slowly a few drops of Fehling's solution. If sugar is present, the 

 liquid will take ,on a yellowish color, and soon a yellowish or reddish precipitate 

 will appear at the bottom of the test tube, (c) Gently heat in water portions of 

 the roots to be tested, then add a few drops of nitric acid. If proteins are present, 

 a yellow color will appear, which turns to a deep orange if some drops of ammonia 

 are added and the whole is again gently heated. 



