CHLOROPHYLL AND GROWTH 125 



cm. were brought through an opening in a 

 glass plate allowed to rest upon the top of 

 the pot in which the plant was grown. The 

 opening around the bud was securely sealed 

 by means of wax, molding clay, or the fol- 

 lowing device : A cork stopper was perfor- 

 ated with an opening larger than the ulti- 

 mate size of the sheathing petioles, and the 

 upper part of the opening was enlarged to 

 form a cup-shaped cavitj^ After the cork had 

 been saturated with paraffin it was placed in 

 the glass plate and enclosing the bud, the 

 bottom of the cup-shaped cavity covered with 

 a loose layer of asbestos or glass-wool, and 

 over this was poured a layer of mercury five 

 millimeters in thickness, which was covered 

 with water to prevent injurious action of the 

 metal. 



This method of sealing exerted no harmful 

 pressure on the plant and allowed it to ex- 

 pand in a normal manner — a very important 

 consideration in experiment where soft- 

 stemmed herbaceous plants were used. The 

 plants were covered with a bell-jar of a capac- 

 ity of four to eight liters sealed to the glass 

 plate, and provided with two tubulures. To 

 one tubulure was fitted a series of potassium 

 tubes or vessels containing potassium hy- 

 drate in solid form, and saturating a mass of 

 asbestos fiber. The second tubulure was con- 



