90 CAROTINOIDS AND RELATED PIGMENTS 



named autumn carotins. Green as well as autumn leaves also con- 

 tain, according to Tswett, colorless water- and alcohol-soluble chromo- 

 gens which form golden yellow salts with acids and alkalies, particu- 

 larly the latter, and which readily oxidize to a brown color. These 

 pigments are regarded by Tswett as playing a part at times in the 

 necrobiotic colorations, and the postmortal colors are held to be due 

 entirely to these pigments. Miss Goerrig's conclusions oppose those 

 of Tswett in indicating that the yellow autumn colors are due in part 

 to the normal unchanged carotinoids of the chloroplastids, diminished 

 somewhat in quantity in comparison with the mid-summer green 

 leaves. Miss Goerrig believes, however, that the chief role is played 

 by new yellow pigments soluble in water. 



Autumn and winter reddening is due at times to red carotinoids. 

 In some cases the red xanthophyll, rhodoxanthin, is involved, e.g., in 

 arbor vitae. In other cases the red carotin, lycopin, is involved, e.g., 

 certain conifers, under tropical conditions. For the most part, how- 

 ever, red autumn colors are due to anthocyanins. 



The vast majority of yellow to orange-red flowers owe their color 

 to chromoplastids containing carotinoids. Very little is known, how- 

 ever, regarding the character and distribution of the individual caro- 

 tinoids among these flowers. In general, floral colors of a primrose or 

 sulfur-yellow color are produced by water-soluble non-carotinoids 

 which are flavones, anthocyanins or related pigments. The latter are 

 usually present in solution in the cell sap in contrast with carotinoids 

 which are present in plastids. The reader is referred to the tables 

 showing the flowers whose color is due chiefly, if not entirely, to 

 carotinoids. 



Carotinoids are undoubtedly the cause of the color of many yellow 

 to orange colored fruits. The reader is referred to the text for the 

 presentation of our present knowledge of this subject. Red tomato 

 fruits are characterized by a red carotinoid called lycopin, which is a 

 chemical isomer of carotin, differing from it only in color and certain 

 physical properties. These relations were recognized first by Millardet 

 (1876) and definitely established by Willstatter and Escher (1910). 

 A. and G. de Negri (1879) first suggested the identity of the water- 

 melon pigment with the red tomato pigment, a supposition finally 

 proved by Monteverde and Lubimenko (1913b). The red pepper pig- 

 ment is also probably lycopin. 



The arils and carpellary tissue of a number of seeds are also char- 

 acterized by carotinoids, carotin, xanthophylls, lycopin and rhodoxan- 



