34 



Elementary Plant Physiology. 



few centimeters. After sufficient gas has been generated and 

 used as above, close the outlet tube by means of the clamp, 

 and the pressure of the gas being liberated will drive the acid 

 back into the second bottle, and action will cease (Fig. 18). 



The above experiment may also be performed by the use of 

 a narrow beaker instead of a retort or respiration tube. The 

 seeds are placed on a thin circular sheet of cork or wood and 

 allowed to rise to the upper end of an inverted beaker filled 



with water, and with the 

 mouth immersed in a 

 dish of mercury. Dis- 

 placement of the water 

 is carried out as 

 above. 



The carbon dioxide 

 used in any of the above 

 experiments excludes 

 the air containing oxy- 

 gen, and it will be in- 

 teresting to note the 

 difference of the action 

 of the seeds in the air 

 and in carbon dioxide. 

 The results would be 

 still more conclusive if 

 the retort containing air should be filled with oxygen. 



25. Influence of ether upon seeds. Provide three 

 bell jars with ground edges, and three strong sheets of glass. 

 Prepare a cerate of equal parts of beeswax and vaseline or 

 lard. Soak thirty grains of corn (Zea) in water for twenty- 

 four hours. Place ten of the seeds in a germinator, or in folds 

 of moist cloth, and put on one of the glass plates. Set by it a 

 beaker containining 100 cubic centimeters of water and one cubic 

 centimeter of sulphuric ether. It may be found more conve- 



Fig. 19. Apparatus for testing influence of 

 ether on germination. A, beaker containing 

 solution of ether and water ; B, bell jar. 



