PIGMENTS 123 



seem to be more favorable to the production of starch. But, in 

 this case also, it is impossible to say whether the pigment is the 

 direct causative agent in the type of carbohydrate production, or 

 whether it is the effect of the same external factors which deter- 

 mine, or modify, the character of the carbohydrate condensation. 



BIOLOGICAL SIGNIFICANCE OF ORNAMENTAL PIGMENTS 



The ornamental pigments undoubtedly have definite biological 

 significance. When present in the storage roots, such as beet- 

 roots, carrots, etc., or in the above-ground parts of plants, they 

 may have served to protect these organs against herbivorous ani- 

 mals which were accustomed to consume green foods. 



In flowers, the brilliant ornamental pigments undoubtedly 

 serve to attract the insects which visit these blossoms in search of 

 nectar, and in so doing promote cross-fertilization. Recent 

 experiments have demonstrated that colors are much more efficient 

 than odors in attracting insects. 



Taken altogether, it is apparent that the pigments may have 

 a variety of important roles in plants. At the same time, some of 

 them may be waste products, with no definite use in the plant 

 economy. 



REFERENCES 



ABDERHALDEN, E. "Biochemisches Handlexikon, Band 6, Farbstoffe der 

 Pflanzen- und der Tierwelt," 390 pages, Berlin, 1911. 



PERKIN, A.G. and EVEREST, A. E. "The Natural Organic Colouring Mat- 

 ters," 655 pages, London, 1918. 



WAKEMEN, NELLIE A. " Pigments of Flowering Plants," in Transactions of 

 the Wisconsin Academy of Sciences, Arts, and Letters, Vol. XIX, Part 

 II, pages 767-906, Madison, Wise., 1919. 



WATSON, E. R. "Colour in Relation to Chemical Constitution," 197 pages, 

 65 figs., 4 plates, London, 1918. 



WHELDALE, M. "The Anthocyan Pigments of Plants," 304 pages, Cam- 

 bridge, 1916. 



WILLSTTATER, R. and STOLL, A. "Untersuchung iiber Chlorophyllen, 

 Methoden und Ergebnisse," 432 pages, 16 figs., Berlin, 1913. 



