56 CAROTINOIDS AND RELATED PIGMENTS 



turned given on treatment with alkali*; that a yellow autumn leaf 

 recovered its green color when immersed in alkali, while green leaves 

 turned yellow and finally red when treated with acids. He accordingly 

 proposed the term polychrome lor the green chromuhi of the leaf 

 which thus changes from green to yellow to red and vice versa, and 

 regarded the phenomena which he oh-crved Q the exact duplication 

 of the yellow and red autumn coloration of leaves. Berzelius (1837a), 

 a little later extracted the yellow color from the autumn leaves of the 

 pear tree ( /'/////* ct>niinnni*\ with alcohol (about 8f> per cent I, and 

 called the pigment xant hophyll. Ber/celius noticed that the pigment 

 readily bit ached, but regarded it as a fat and a- beiim derived from 

 the green piument of the leaf. He was careful to distinguish (1837b) 

 between the pigment xanthophyll and the red pigment which could 

 be extracted from the red autumn leave- of the mountain ash (Xorbnx 

 <iitciij>(iri(i\ and cherry tree.- i /'///////* c> /V/.S//M . and from the red 

 autumn leaves of gooseberry (Hilm* <ilosxnl(n-i<i, var. ruhr<i) and com- 

 mon barberry (Ii< rl>< ri* rulij<irix\ bushes, which pigment Berzelius 

 called erythrophyll. 



Following the-e very early experiment- which were carried out 

 before the development of our prc-ent-day knowledge of the yellow 

 chromolipoids one tinds a number of more or less unrelated observa- 

 tion;- reuardinti the yellow autumn colors, which were made incidental 

 to some of the plant piument studies which have already been reviewed 

 in connection with the carotinoids in the chlorophtstid. For example, 

 Fremy ilSGOi regarded the autumn coloration as due to his phylloxan- 

 thine, the isolation and properties of which were described in an 

 earlier paragraph. As already pointed out, Fremy believed that two 

 pigments existed in green leaves, a reenish-blue phyllocyanine and 

 a yellow phylloxanthine, and that the autumn colors were the result 

 of the fact that the latter pigment was more stable than the former. 

 Sachs (1863) made a microscopic study of leaves during the autumn 

 color change and proposed the theory that the chlorophyll migrates 

 out of the plastids leaving behind a larger number of intensely yellow 

 granules. The latter were actually observed and were soluble in 

 alcohol. Mer (1873), however, was not able to substantiate this 

 belief regarding a migration of the green granules out of the leaf cells, 

 but the presence of yellow or brownish-yellow plastids in the cells of 

 the autumn colored leaves, at least in the necrobiotic 4 phase, is well 



* According to Tswett (1908 c) the autumn coloration occurs in two phases, namely, 

 the necrobiotic and the postmortal. The former is always characterized hy a yellowing 



