1915] B. Horowitz 167 



material still awaiting further study. It follows f rom this that no 

 clearly-defined chemical relationships between many of the pignients 

 can be traced. The many theories regarding the origin of plant 

 pigments — Chlorophyll in particular — have lost much of their force 

 as a result of a more detailed study of the chemistry of the pig- 

 ments. Nothing analogous to Baeyer's beautiful conception of 

 sugar synthesis f rom f ormaldehyde has been traced f or Chlorophyll. 

 Perhaps ere long the master mind of Willstätter will have added 

 this achievement to his many others. 



From the purely genetic Standpoint colors in flowers, especially 

 those due to anthocyanin, may be traced to the following factors :^* 

 C, a chromogen, colored or not colored — possibly a glucosidal 



flavone. 

 E, an enzyme (oxidase) which acts on C and produces color, giving 



product X. 

 e, another enzyme, which acts on X, giving product Y, which dif- 



fers in color from X. 

 'A, an anti-oxidase, which inhibits the action of E. 

 R, reductase, which does the exact opposite to that of the enzyme E. 



" If a flower only possesses C or E, then the color will be white 

 or pale yellow, according to the color of the chromogen, if present. 

 If the flower with the factor C be crossed with a flower with the 

 factor E, then the color of the flowers of the offspring will be red, 

 or a deeper color, if e also be present. If either ^ or i? be present, 

 then there will be no difference in the flowers of the offspring as 

 compared with the parents." 



Palladin, in developing his conception of the röle coloring mat- 

 ters play in respiratory activity of plants, has this to say:^^ "In 

 plants are to be found pro-chromogens which may be regarded as 

 glucosides, or decomposition products of proteins. Enzymes con- 

 vert the pro-chromogens to chromogens. Oxidases act on the chro- 

 mogen (in the presence of oxygen) yielding pigments which re- 

 ductases are capable of reducing again. For example, an oxidase 

 can convert Carotin, C40H56, into xanthophyll, C40H56O2, a reduc- 

 tase being able to reconvert the latter into the former." 



^* Haas and Hill : Chemistry of plant products, 1913, p. 243. 

 15 Haas and Hill: Ihid., 1913, p. 251. 



