Show characteristic characteristics of plants times at which different plant plants open and shut their petals have beon investigated and it ie Is commonly found that the hour varies according to the amount ct of moi moisture in the air the main thing la to to protect the pollen from invading moisture and since some plants such aa as the pimpernel promptly close their petals on the neat approach of ofrain rain they serve as er glasses some plants seem to believe in a short days work vork the pimpernel for instance opening at 8 in the morn ing and closing at 2 in the afternoon the goate beard on the other hand doing L business iness from 2 a m to 10 p m |