3 i6 



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 little paste, in water, of cornstarch or wheat 



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



a little potassium iodide 

 * added, or of a tincture 

 of iodine. On the ap- 

 plication 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 corn, in a grain of 



* FIG. 1 19. Diagram of a Section of a Green Leaf . 



ep., epidermis; c., cells with chlorophyll grains; i., intercel- WnCat, Or in a 

 lularspaces; a., air chambers ; *.>.. breathing pores. *^ QW 



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 will 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. 



