66 THE NATURE AND WORK OF PLANTS 



Virginia creeper, columbine ; and a cutting composed 

 of a large branch or twig should have the lower end 

 immersed in a stone or glass jar as in the water cul- 

 tures previously described, § 13. The jars should be 

 filled with water from a stream or well to which an 

 ounce of sugar or glucose has been added for each 

 quart. Compare the colors of the leaves with others 

 grown in the same kind of water without sugar, and 

 also with those remaining on the plant. 



This experiment may be repeated if living speci- 

 mens of the bladderwort (Utricularia) can be pro- 

 cured. Place some specimens in a shallow dish of 

 water and set in the sun. Prepare a second dish, but 

 add the proportion of sugar used in the last test. 

 Change the liquids at least once a week. Note the 

 depth of red color of the two specimens. Cold and 

 wounds also induce the formation of red coloring 

 matter. 



77. Changes in color. — The red and blue colors 

 appear to be very closely connected, because the 

 parts of a plant may often change from one to the 

 other in the course of a few days. This may be 

 noticed in the flowers of the peony, as well as in the 

 opening buds of many plants. Note the color of 



