82 



The Living Plant 



be proven by experiments, too elaborate, however, for description 

 at this place. Furthermore, as we may conveniently note here, 

 all of these same working parts are simultaneously releasing water 

 as well. It is therefore true, as a general principle, that all working 



parts of all plants are 

 giving off carbon dioxide 

 as well as water, pre- 

 cisely as animals are do- 

 ing. 



But do plants exhibit 

 the other phenomenon 

 of animal respiration, — 

 absorption of oxygen? 

 It is very easy to prove 

 that plants must have 

 oxygen in order to live 

 and work, precisely as 

 animals must; for if two 

 sets of the same seeds are 

 placed in two similar 

 closed chambers, and 

 then the oxygen is re- 

 moved from one chamber 

 by a chemical absorbent 

 while it is left untouched 

 , , , . , . , in the other, the seeds in 



Fig. 28. — Two similar tube-chambers in which were 



placed similar sets of germinating oats kept wet the OXygeulcSS chamber 

 and in place by wads of moss, and treated pre- . 4- n 



cisely alike except that those on the right were dc- Will UOt gCrnunate at all 



prived of oxygen. ^^^ ^|j| ^^^^ ^-^^ ^j^-j^ • ^^ 



the other they will grow normally for a considerable time (figure 

 28). Furthermore, if the air of a closed chamber in which seeds 

 have been growing for some days be subjected to chemical 

 analysis, it is found that most of the oxygen has disappeared 

 from the chamber, and must therefore have been absorbed by 



