THE PHYSIOLOGY OF COLOR IN PLANTS. 



73 



served by many of the coloring substances besides chlorophyll 

 are by no means secondary in distribution or importance to the 

 individual plant to the exterior adaptations described above. 



The principal coloring matters among the higher plants besides 

 chlorophyll (leaf- green) are those which have been grouped under 

 the terms erythrophyll, xanthophyll, and anthocyan. Of these 

 substances the chemical and physical properties of chlorophyll 

 are best known, although its exact composition is yet undeter- 

 mined. Not only is our chemical knowledge of the non-green 

 colors very vague, but it is thought that a great number of differ- 

 ent substances are grouped under each of the above and other 

 color terms. Thus, for instance, anthocyan is made to include the 

 large number of substances to which are due the red, blue, violet, 



a B C 



III. 



Fig. 



1. I. Spectrum of Chlorophyll showing Seven Absorption Bands. The two in the 

 red-yellow between B and D, and the three in the blue- violet, beyond F, are the most 

 important and characteristic. The bands between D and E are most marked in the spectra 

 of solutions which have been exposed to the air and light some time, and are believed to 

 be due to disintegration products of chlorophyll. 



II. Spectrum op Amaranth-red. All the rays except those falling between B and D 

 have been absorbed. 



III. Spectrum of Autumnal Color of Leaves of Ampelopsis. All the rays except a 

 part of those falling between C and D have been absorbed. 



and purple colors of such plants as the violet, beet, canna, rose 

 and amaranth. Only so much is known of the formation of these 

 color substances as to justify the assertion that many of them 

 are produced as disintegration products of the glucosides and 

 others from a mother substance chromogen. 



The coloring matters of plants may be in solution in the cell 

 sap as in the beet and amaranth, in irregular solid masses in the 

 sap or protoplasm, as in nasturtium (Tropwolum) ; or may be in- 

 corporated in the cell wall, as in logwood (Hcematoxylon) ; or 



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