The Response of Plants 151 



like good children ; they go to sleep at dusk and rise with 

 dawn. The difference in illumination merely gives no- 

 tice that time has arrived when the plant should act in a 

 special way. Darwin has shown us that if for any rea- 

 son ' ' the leaves have not been brightly illumined during 

 the day" the nervous little things fail to sleep at night. 

 And away north "where the sun does not set, the trans- 

 ported southern Mimosa still regularly goes to sleep. " 

 Furthermore its habits may be changed, so that it will 

 sleep by day and wake by night. Plants brought to our 

 greenhouses from the other side of the world instead of 

 bringing with them their waking and sleeping schedule 

 of hours, actually conform to the dial of the meridian 

 to which they have arrived, and sleep and wake with the 

 local population. Could conformity go farther ? 



But it is time we turned to another chapter in this 

 argument. The response of the plant to the world of 

 animals is the latest accomplishment of the vegetable 

 economy. So rich, so wonderful, so varied is this re- 

 sponse that a whole library might be gathered of books 

 discussing this single topic. The whole array of flowers 

 with all their brilliancy of color, beauty of form, and 

 absolute perfection of sweetness and perfume is but a 

 recognition by the plant that other creatures too can 

 taste the light and know its sweetness. Here is a re- 

 sponse to creatures that have eyes and noses. Nowhere 

 color in this world of plants but somewhere is an eye to 

 see it ; nowhere odor, but somewhere a nose to inhale its 

 fragrance. 

 ' ' Full many a flower, ' ' you say, * ' is born to blush unseen 



And waste its fragrance on the desert air. ' ' 



