i4 NATURE I IF CHD >R< IPHYLL 



surrounded by earth or the light is excluded from them by some 

 other means; chlorophyll disappears from the plastids and fails 

 to develop in the new cells that are formed in the dark. Plants 

 in which the chlorophyll is not developed are said to be etiolated. 

 The plastids are in the cells, however, for if an etiolated seed- 

 ling is removed from the dark to the light the chlorophyll will 

 begin to appear in a few hours. The greening of potatoes when 

 removed from the ground and left in a strong light is a familiar 

 example of this. It is evident that the formation of chlorophyll 

 is closely connected with the action of light. Another impor- 

 tant point regarding the influence of light is the fact that such 

 a food as starch is not usually found in the leaf in the absenc< 

 of light. This may he easily verified by cutting the initials of 

 your name in rather large letters from a piece of black paper or 

 smooth tin-foil and fastening the letters in the early morning 

 with mucilage to the upper surface of a well-sunned leaf of a 

 starch forming plant. Before the sunlight fades remove the 

 leaf from the plant and place it in alcohol. This will dissolve 

 th«- chlorophyll and the leaf will become quite white in a few 

 hours. Now place the leaf in a tincture of iodine which turns 

 starch to a blue or blue-black color. Wherever the light was 

 excluded from the leaf by the letters there is only a pale yellow 

 color but all portions of the sunned leaf show an abundance of 

 starch as revealed by the bine or blue-black coloration. Xo 

 Starch can he detected in leaves taken from plants that have hern 



growing in the dark for twenty-four hours. Plastids that do 



not contain chlorophyll, examples of which are found in the 



cells forming the white bands or blotches in many variej 

 plants, do not form starch in the light. It is evident from these 



facts that the chlorophyll and light co-operate in some wa\ in 



tin- formation of starch. It is known that chlorophyll absorbs 



tain portion of tin- sunlight. If a beam of sunlight i< 



Caused to pa^s through a prism it is separated into seven colors, 



ted. orange, yellow, green, blue, indigo and violet. When, 

 however, a beam first passes through an alcoholic solution of 

 chlorophyll or through a green leaf a portion of certain colors 



and all of other colors do not appear. The chlorophyll has taken 



