132 



GYPSUM METHOD. 



[CH. V 



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

 is turned upside down and the root (which projects 



FIG. 25. Exp. 152. Copied from Pfeffer. 



vertically upwards) is covered with soft gypsum. A piece 

 of waxed paper in which a hole has been made (with a 

 hot needle) is slipped over the tip of the root and pressed 

 down with a bored glass plate. In this way the block of 

 gypsum a is formed ; when it is sufficiently set, the waxed 

 paper is removed, and for it is substituted a piece of wet 

 tissue-paper on which the block b is added. The form of the 



