158 FREAKS OF PLANT LIFE. 



the tip determines the upper growing part to bend 

 either from or to the exciting cause. A radicle may 

 be compared with a burrowing animal, such as a mole, 

 which wishes to penetrate perpendicularly down into 

 the ground. By continually moving his head from 

 side to side, or circumnutating, he will feel any 

 stone or other obstacle, as well as any difference in 

 the hardness of the soil, and he will turn from that 

 side ; if the earth is damper on one than on the other 

 side he will turn thitherward as a better hunting- 

 ground. Nevertheless, after each interruption, guided 

 by the sense of gravity, he wall be able to recover 

 his downward course, and to burrow to a greater 

 depth."! 



From seedlings wc are led to mature plants, and 

 here again we encounter systematic rotatory move- 

 ment so universal in its character that it is doubtful 

 if it does not exist more or less in all plants. 



A hybrid raspberry, about a foot high, that was 

 growing vigorously, was watched in the month of 

 March. During the morning the growing point of 

 the stem almost completed a circle, and then de- 

 flected to the right. In the afternoon it reversed its 

 course, and continued to move in that direction for 

 forty hours. 



Some young ivy-plants were seen to rotate their 



' Darwin, " Movements of Plants," p. 200. 



