The Kinds of Work That Are Done by Plants 83 



the seeds. And the same thing is true no matter what structures 

 we place in the chamber (saving only an apparent exception, 

 soon to be noted, in the case of lighted green leaves), and no 

 matter whether the chamber is exposed to the light or kept in 

 the dark. It is evident, therefore, that all parts of working, 

 (and that is to say, of living) plants, absorb oxygen and release 

 carbon dioxide precisely as animals do. 



There is no one, I think, who can grasp fully the bearings of a 

 complicated subject after only a single presentation, no matter 

 how clear this may be. It is therefore quite likely that some reader 

 ere this has experienced a feeling of dazement, and been led to 

 exclaim, along with the much-puzzled German, ^'Jemand ist 

 verriickt, aber wer?"; and he may even inchne to imagine that 

 I am the ''wer." For have not I shown, in an earlier elaborate 

 chapter, that plants absorb carbon dioxide and release oxygen, 

 while now I have proven by evidence quite as conclusive that 

 they do exactly the opposite? But there is, nevertheless, no in- 

 consistency. For the reader will recall that it is only the green 

 tissues which absorb carbon dioxide and release oxygen, and then 

 only in light, and then only from the tiny little chlorophyll grains 

 embedded inside of the protoplasm. There should therefore be 

 no trouble in understanding how the protoplasm in which those 

 grains are embedded, like all other living parts of the plant, can 

 be respiring, while the chlorophyll grains alone are engaged in the 

 photosynthetic process. The case of the chlorophyll grains, 

 however, is not so simple as my statement implies, because, 

 since they are living protoplasm, there is every reason to think 

 that they also respire even m light, and that in them, — and in 

 them alone, — the two processes go on together. If, now, photo- 

 synthesis and respiration, with their exactly opposite gas ex- 

 changes, proceed together in leaves, why do they not neutralize 

 one another's results? The answer is easy. Experiment shows 

 that on the average the photosynthesis in green leaves in the 

 light is over twelve times as active as respiration (and it may rise 



