THE LEAVES 65 



ing a small aquatic plant in a tumbler, or the leaf of 

 a land plant may be immersed in water and the 

 formation of the bubbles noted. 



75. Non-green colors. — If the experiment in § 72 

 is repeated, it may be seen that red and other colors 

 are formed in leaves grown in darkness as well as 

 in light. This may be illustrated still further if a 

 flowering branch of some plant is thrust through a 

 hole in the wall of a tight pasteboard box, and the 

 flowers allowed to open in darkness. The most 

 noticeable of the colors that are found in leaves, 

 beside green, is red, though purples are also abundant. 

 All shades of red, blue, and yellow are to be seen in 

 flowers and fruits. If a clump of rhubarb is made to 

 grow in a dark cellar, the leaves and stems will be 

 blood red. 



76. Origin of red colors. — Red coloring matter 

 is formed most freely in parts of the plant contain- 

 ing much sugar. The origin of coloring matters is 

 not well understood. It has been determined, how- 

 ever, that when a specimen is fed with sugar, it will 

 manufacture this color more abundantly. To demon- 

 strate this action a species should be selected that 

 has the power of making the color, such as ivy, 



