Two students in biology wanted to find out which plant required more water, an annual or a perennial flower. They decided to use a dandelion as the annual and a rose as the perennial.  In three separate test tubes they placed equal amounts of water.  In the first two test tubes they placed the dandelion and the rose, leaving the third test tube without a flower as a control.  Before placing the flowers in the test tubes they cut the stems at an angle.  After two days they recorded the amount of water left in the test tubes.