120 



GYPSUM METHOD. 



[CH. V 



The degree of compression, and therefore the force 

 exerted, is estimated by reading, with a horizontal 

 microscope, the distance between the needle points fitted 

 to the inside of the spring. 



The following is the method of fitting the plant into 

 the apparatus. 



Fig. 23, Exp. 152. 



The seedling bean is placed in the flower-pot n filled 

 with damp sawdust so that 15 — 30 mm. of the root 

 project through the hole. A lid is placed on the pot, which 



