FLOWER PIGMENTS. 



BY C. M. BROOM ALL. 



The brilliancy and variety of color of the flowers that 

 surround us cannot fail to excite a desire to know something 

 of the pigments that produce these hues. Unfortunately, 

 however, this is a subject about which there is much to learn, 

 as is evidenced b}^ the comparatively scant literature relating 

 thereto and the absence of a concensus of opinion regarding 

 the chemical and physiological relations of the pigments. 



In connection with the chemico-physiological side of the 

 question it is interesting to call attention to certain color 

 changes produced in flower pigments by very simple chemical 

 means. These reactions have probabh- been noted by most 

 students of plant physiology, and indeed it is only by reason 

 of their commonness that they are of interest. As will appear 

 later, the}' give promising food for speculation concerning the 

 chemistr}' and ph^'siology of plant life. 



A few easily performed tests with the pigments as extracted 

 from man}' kinds of flowers, both cultivated and wild, will 

 exhibit certain reactions common to the flowers of a given 

 color. Thus, if an alcoholic extract is made of the petals of 

 a flower, we find it to exhibit, at least in the great majority of 

 the cases, the property of changing color as the reaction of 

 the solution changes. In other words, the alcoholic solution 

 makes what chemists call an " indicator ; " that is, a solution 

 which turns one color when a drop of alkali is added, and 

 another color with a drop of acid. These changes are corre- 

 lated with the natural color of the flower experimented upon. 

 In the tests by the writer, sodium hydroxide and nitric acid 

 were found to be verj^ satisfactory reagents, although care 

 had to be exercised not to add an excess. Of course, other 

 acids and alkalis will also answer. 



A series of tests covering a very considerable number of 

 both wild and cultivated plants indicates the color reactions 

 which follow as applicable to the variously colored flowers. 



