GETTING ES TA BUSHED 



73 



(about one inch in diameter) , one of which fits inside 

 the other; cut off the smaller one as shown in the 

 figure and make a spiral spring of the same diameter. 

 (The spring is easily made by winding a piece of 

 brass wire, about No. 18, closely* and evenly around a 

 spool.) In a piece of board (which should be about 

 an inch thick) bore a hole large enough to snugly fit 

 the larger bottle. Support this by two blocks (as 

 shown in the figure) , so that it may hold the bottle in a 

 vertical position. Allow the 

 plant to grow up into the 

 smaller bottle and press up- 

 ward against the spring: put 

 a little cotton in the bottle 

 as a cushion for the plant to 

 press against. A suitable 

 weight (about two pounds) 

 must be placed on the ap- 

 paratus ; sufficient earth 

 should be removed at the 

 bottom of the bottle to allow 

 access of air. Each day 

 mark on the outside of the 

 larger bottle the height to 

 which the inner bottle has 

 been raised (a strip of paper 

 gummed to the outer bottle 



\ TTTI 59 - Apparatus for measuring the force 



Will Serve for thlS). When O f the inward growth of the plant. 



