THE POWER OF MOTION. 



CHAPTER 11. 

 THE POWER OF MOTION IN PLANTS. 



It would be foreign to the object of this work to say much on 

 this interesting subject. Eeference has previously been made to 

 the motion of protoplasm in living cells, to the closing and 

 opening of the leaves when dried or moistened, and the growth of 

 nodes on the lower side to aid in straightening up a culm which 

 has fallen down. The following will serve to illustrate what may 

 not be new to all of the readers of these pages : 



A thrifty hop-vine went Avinding u\) nine or ten feet to the top 

 of a stake, and then four feet and two inches above any support, 

 when it tipped over in the direction of the prevailing wind. It 

 swung slowly around, sometimes making a revolution in from 

 one to two hours. If another stick be within reach of the 

 revolving top, it will seize the support and go on climbing as 

 before. 



Every one knows that asparagus or celery, placed on the side, 

 will soon show the tif)s bending upward, and that the stems and 

 leaves of a geranium set in the window will soon bend towards 

 the light. These are familiar, and on that account may not 

 awaken much curiosity, but it must seem wonderful to learn, for 

 the first time, that the power of moving in circles or ellipses, or 

 zigzag lines, is universal, so far as we know, to all young growing 

 stems and all their branches. The same is true of the young 

 leaves and all of the young roots. "Every growing part of 

 every plant is continually circumnutating or bowing around." 

 (Darwin). This motion is produced by the increased turgescence 

 of the cells, together with the extensibility of their cell-walls on 

 tlie convex side. 



As Darwin says, " It would appear as if the changes in the 

 cells required periods of rest. A young root may be 



