3i6 



NATURE-STUDY 



is thus seen to be a condition necessary for the formation of 

 the green color of plants. 



This green color is not due to a green liquid in the cells 

 of the plant, but to little green grains called chlorophyll— 

 leaf-green. These may be seen nicely in moss-leaves under 

 the compound microscope. 



Make a httle paste, in water, of cornstarch or wheat 

 flour, and add a few drops of a solution of iodine with 



a httle potassium iodide 

 I added, or of a tincture 



of iodine. On the ap- 

 phcation of this solution 

 the starch of the corn- 

 starch and flour turns 

 deep blue. This is a 

 test for starch. Test 

 for starch in a kernel 

 of com, in a grain of 

 wheat, or in a potato. 

 Now get some varie- 

 gated leaves, such as those of the white-bordered geranium. 

 Boil a few minutes in water, and then soak in strong al- 

 cohol for several minutes. This dissolves out the chloro- 

 phyll. The solution with the alcohol may have to be re- 

 peated before the leaf is quite bleached. Now place the 

 leaf in the solution of iodine and potassium iodide. The 

 part that was green before wiU now turn blue, while the 

 former white border will remain so. This proves that 

 the starch was formed only in the green part of the leaf. 

 Starch forms where there is chlorophyll, and as a rule not 

 elsewhere. 



Fig. 119. Diagram of a Section of a Green Leaf. 



ep., epidermis ; c, cells witli chlorophyll grains; i., intercel- 

 lular spaces; a., air chambers ; <*.>., breathing pores. 



