RESPIRA TION. 



95 



hat oxygen has entered, we may use the vessel for another experiment, 

 >r set up a new one to be used in the course of 12 to 24 hours, after the oxy- 

 gen has been consumed. Place some folded damp filter paper on the ger- 

 minating peas in the jar. Upon this place one-half dozen peas which have 

 ust been germinated, and in which the roots are about 2Q-2$mm long. See 

 igures 73, 74. The vessel should be covered tightly again and set aside in a 



Fiff. 73- Fig- 74- Fig. 74*. Fig. 73a. 



Fig. 73.— Seedlings in vessels containing an excess of carbon dioxide, and very little 

 >xygen. No growth takes place. 



Fig. 74. — Vessel with normal air used as a check. No excess of carbon dioxide, usual 

 .mount of oxygen. Normal growth takes place. 



Figures 73d and 74*2 represent the condition of the peas in the experiment shown in figs. 

 3 and 74, a month later. The cylinders as set up for that experiment were left for a 

 nonth and then photographed^ The peas in the cylinder containing normal air have 

 ;rown, producing stems which reach to the top of the cylinder, while in fig-. 730;, where 

 he oxygen wasabsent, the peas have died. At this time a test was made with a lighted 

 aper ; it burned brightly in the cylinder 74^, but was quickly extinguished in the cylinder 

 3«. The peas having died in this jar, decomposition had taken place and other gases than 

 arbon dioxide were present, but there was not sufficient oxygen to support combustion. 



rarm room. A second jar with water in the bottom instead of the gcrminat- 

 ng peas should be set up as a check. Damp folded filter paper should be 

 upported above the water, and on this should be placed one-half dozen peas 

 pith roots of the same length as those in the jar containing carbon dioxide. 



