LABORATORY EXERCISES 73 



25. Osmosis. 



Materials. Potato, thistle tube, parchment paper, bladder, salt. 

 Perform the experiment described on page 65. 



26. Root-Hairs. 



Materials. Compound microscope, roots of oats, clover or other 

 seeds germinated between blotters. (Page 64.) 



Examine the root-hairs and make drawings of them. How many 

 celled are they? How do they differ from roots? 



27. Stored Food in Twigs. 



During the winter collect some branches of trees two or three feet 

 long. Place them in water, change the water occasionally. Note how 

 much growth takes place. Where did the food material come from? 

 What relation has this to orchard management? 



28. Tests for Proteids. 



Materials. Nitric acid, ammonia, seeds. 



All proteids (and a few other substances) are turned yellow by 

 nitric acid. This is why one's fingers are made yellow when working 

 with nitric acid in the laboratory. This yellow color becomes deeper 

 when moistened with ammonia. 



Cut several cross sections of corn, beans and other seeds. Make 

 the protein tests. Which part of the kernel of corn contains the most 

 protin? Do beans or corn appear to contain the larger amount? 



29. Tests for Starch. 



Materials. lodin solution, seeds. 



Test corn, beans and other seeds for starch. Which part of the 

 kernel of corn contains most starch? 



30. Microscopic Examination of Starch. 



Materials. Compound microscope, iodin solution, corn, potatoes, 



etc. 



Examine sections of corn and potatoes. (X about 500.) 



Make drawings of the starch grains. Compare the shapes and sizes 



from different plants. Notice how the grains are arranged in the cells. 



Add a drop of iodin solution to the different slides and note the 



effect. 



