CAROTINOIDS IN THE PHANEROGAMS 61 



benzene layer of the Gregor Kraus separation, and it was not turned 

 blue by acids. 



C. A. Schunck's (1903) splendid spectroscopic observations of the 

 xanthophylla included an examination of the pigments of yellow 

 autumn leaves. The method of preparation of the material for these 

 studies, which has already been described, precludes the presence of 

 pigments other than carotinoids in the alcoholic solution submitted to 

 Schunck's carbon disulfide separation. Schunck does not mention 

 chrypophyll (carotin) in connection with his autumn leaf examination, 

 but his xanthophyll solution gave four banded spectra in practically 

 all cases. The conclusion drawn was that autumn coloration is due 

 to L. xanthophyll and a preponderance of the acid derivative of B. 

 xanthophyll, which is characterized by a four banded spectrum, a 

 result which strongly supports the idea that certain changes do occur 

 among the carotinoids of the leaf during the necrobiotic period. 



Kohl (1902h) made a careful study of autumn pigmentation and 

 ascribed the autumn colors to carotin, a xanthophyll (showing a four 

 banded spectrum (see Schunck)), (3 xanthophyll (a water soluble pig- 

 ment with no spectroscopic properties), a little phyllofuscin and a 

 small amount of another yellow pigment also derived from chlorophyll, 

 which he does not name. One must agree with Tswett (1908b), how- 

 ever, that Kohl's methods are open to serious objection, in that the 

 preliminary boiling of the leaves in water, before the extraction of the 

 pigments with hot alcoholic potash undoubtedly brought about serious 

 decompositions because of the high acidity of the cell sap in autumn 

 leaves. Nevertheless, Kohl's observations do indicate that carotinoids 

 may be expected to decline noticeably during the autumn color change, 

 thus confirming the belief expressed by Tschirch (1884). Kohl states 

 that it is sometimes difficult to demonstrate the presence of carotin 

 (carotinoids) at all in autumn leaves, and concludes that the intense 

 yellow color of some autumn leaves is due to the formation of other 

 yellow pigments. 



Tswett's (1908b) study of the pigments of yellow autumn foliage 

 appears to be the most reliable which we have available at present on 

 which to base a definite knowledge of the autumn yellow colors. It 

 is true that Miss Goerrig's (1917) more recent study gave quite oppos- 

 ing results in some particulars, but the apparent contradictions are 

 not wholly irreconcilable when one takes into account the fact that 

 Tswett's and Miss Goerrig's studies differ in at least two very sig- 

 nificant points, namely, (1) Tswett studied the pigments in fresh 



