Show characteristics of plants times at which different plants open and shut their petals have been investigated and it Is commonly found that the hour varies according to the amount of moisture in the air the main thing Is to protect the pollen from invading moisture and since some plants such as the PIT pimpernel pernel promptly close their petals on the near app approach TORCh of rain they serve as er glasses some plants seem to believe in a short days work the pimpernel tor for instance opening at 8 in the morning and closing at 2 in the afternoon the on the other hand doing business from 3 a in to 10 p m |