21.   The flowers have never opened.

22.   The summer sun rises earlier and sets later the farther north you are, and flowers open and close earlier, too.

23.   These flowers generally open for four to five weeks, starting in early July.

24.   We watched a cactus flower open as the morning sun moved across it.

25.   What causes these flowers to open before dawn is a combination of light and temperature signals.

26.   When the flowers opened, I found petal blight on every blossom.

27.   With a proper cool period, the stalk will grow longer and the flowers will open in the right sequence, from bottom to top.