The Prevalence of Green Color in Plants 



37 



So striking and far-reaching are the conclusions already reached 

 in this chapter that anything added thereto must come as a kind 

 of anti-climax; and therefore I wish we could stop just here. 

 Moreover the chapter is al- 

 ready over-long, though no 

 longer, I maintain, than the 

 relative importance of its 

 subject sufficiently justifies, 

 especially as it seemed to me 

 best to make this first treat- 

 ment of very important top- 

 ics illustrate the methods 

 through which our scientific 

 knowledge has been gained. 

 Yet several closely related 

 matters, especially concern- 

 ing the colors of plants, 

 should have our attention 

 before we depart from this 

 subject, though I venture to 

 suggest to the reader that he 

 should not attempt to read 

 all of this chapter at one 

 sitting, but reserve the fol- ^ ^ , ,. , ^u ^ . ^u ^■ 



°' Fig. 6. — A diagram of the photosynthetic ma- 



lowing part for a time by chinery, showing the parts reduced to the low- 

 est possible terms, viz., a single living cell, with 

 a single chlorophyll grain, a water-carrying 

 duct (on the left) and a sugar-carrying sieve- 

 tube (on the right) ; shading is protoplasm. 

 be dismissed very briefly. The circles are water; the squares are carbon 



*^ dioxide; the triangles are oxygen; the crosses 



Is it quite clear to the reader are grape sugar; the arrows show the direc- 



^ . tions of movement. 



why chlorophyll looks green Cells magnified about 200 and molecules about 



to the eye? This, indeed, ---n-- times. 



is told very plainly by the spectroscope, when it shows that 

 chlorophyll, in stopping the useful red and blue rays from 

 the light of the sun, allows the other and useless rays to 



itself. 



One of these matters may 



