152 FREAKS OF PLANT LIFE. 



early in its career active spontaneous motion com- 

 mences. It is true that the oscillations may seem 

 small to the unaided eye, being only about one- 

 twentieth of an inch, or less, in the garden bean, on 

 each side of a central line, but nevertheless distinct 

 and decided. Rootlets were induced to grow down 

 sloping plates of smoked glass, on which their own 

 vibrations were traced, and thus they recorded the 

 extent of their own lateral motion. This rotation of 

 the young radicle seems to be almost universal, when- 

 ever not prevented, or until prevented, by the close 

 pressure of the soil. In a loose soil, or when entering 

 worm-holes, this oscillation would doubtless be useful 

 in enabling the root to enter the ground. The bean 

 having been selected for experiment it was shown 

 that the following is an explanation of how the root 

 enters the earth. 



" The apex (of the radicle) is pointed, and is pro- 

 tected by the root-cap ; the terminal growing part is 

 rigid, and increases in length with a force equal, as 

 far as our observations can be trusted, to the pressure 

 of at least a quarter of a pound, probably with a 

 much greater force when prevented from bending to 

 any side by the surrounding earth. Whilst thus 

 increasing in length it increases in thickness, pushing 

 away the damp earth on all sides with a force of 

 above eight pounds in one case, of three pounds in 

 another case. It was impossible to decide whether 



