EFFECT OF LIGHT ON PLANTS. 175 



but they are very weak, and trail upon the ground. 

 I have myself seen plants, which had grown in 

 dark rooms or cellars, and were perfectly white, 

 gradually become green on being exposed to the 

 light. 



EDWARD. 



Then does the gardener cover up endive and 

 celery with earth, to make them grow white ? 



MOTHER. 



He does, my dear ; and earthing them up in 

 this manner is called blanching. The position of 

 the leaves of plants depends in some measure on 

 their exposure to light, to which they always turn 

 their upper surface; and it has been remarked, 

 that the ripe ears of corn, which bend down with 

 the weight of the grain, scarcely ever incline to 

 the north, but always turn towards the sun, or to 

 the south; you may observe this yourself in a field 

 of ripe corn. The opening of flowers is also 

 effected by light : many of them do not expand 

 their petals fully except when the sun shines, 

 and therefore open them during the day, and shut 

 them at night, alternately. There are some 

 flowers, however, which open only in darkness, 

 and shut up their blossoms on the approach of 

 light : M. Decandolle, a French botanist, who 

 tried some curious experiments on the subject, 

 found that the Mirab'ilis Jal'apa, Marvel of Peru? 



