But as soon as people began to study the life and the ways of plants more thoroughly, they found out that this was not at all correct. Plants most certainly can move. No one who has watched a sundew curl its tentacles over a captured fly, or the leaves of Venus's flytrap snap together the instant an insect touches its sensitive hairs, can have any doubt about it. But, of course, plants do not move to the same extent that animals do.
Plants only move when there is something to be gained by doing so.
As a rule they are fast-rooted in the soil, and they find all the food they need in the sunlit air around them and the soft rain that falls upon them, so there is no occasion for them to move. But when on account of the poorness of the soil they cannot get enough nourishment, certain plants have learned to move, just as many lower animals do, in order to obtain for themselves a sufficient supply of nitrogen. But it is not only to obtain food that plants move. Many plants alter their position when they go to sleep at night. Notice how the pansy in the garden bed bends down its head when evening comes, how the daisy draws its ray flowers over the delicate disk flowers in the center of its head.