64 CAROTINOIDS AND RELATED PIGMENTS 



phases, determining colorimetrically carotin and xanthophylls (a* a 



group) by the AVillstiitter and Stoll (1913c) method, using potassium 

 dichromate IIP standard. The study was necessarily most exacting and 

 laborious. In general, the data show that the amount of autumn 

 rarotinoids in comparison with the rarotinoids in the green leaves just 

 before the nerrobiosis varies with the kind of plant and the character 

 of the weather during the latter period, sometimes being more and 

 sometimes less, but that the autumn carotinoids, even when higher 

 than the prencerosis pigments, never equal quantitatively those pres- 

 ent in the leaf in midsummer. In all cases the xanthophylls exceed 

 the carotin. The reader is referred to the original paper for other 

 details. The plant? examined arc noted in Tables 1 and 2. 



From a qualitative standpoint Miss fioerrie's results differ signifi- 

 cantly from Tswctt's in two particulars, (1) the former denies the 

 existence in autumn yellow leaves of carotinoids differing from the 

 normal plastid carotinoids, (2) and find* water-soluble pigments in 

 abundance so that, ""When one compares the color of the extracted 

 meal and the wash waters with the meal before extraction a good idea 

 is obtained of the frequently small significance of carotin and xan- 

 thophylls in the autumn leaf pigmentation." 



With regard to the first differ- -n.-e. Mi- Ooerrig's rondusion is cer- 

 tainly open to criticism in that she did not submit her carotin and 

 xanthophyll fraction-;, obtained by reparation between alcohol and 

 petroleum ether, to any confirmatory testa whatsoever. That Mis 

 Ooerrig's carotinoids from autumn leaves were probably the same as 

 the mixture which Tswett calls autumn xanthophylls is indicated by 

 the very significant -tatement that repeated extractions of the petro- 

 leum ether solutions with high percentage methyl alcohol were fre- 

 quently required to separate the xanthophylls from the carotin. It is 

 not difficult to conjecture that such xanthophylls, like Tswett's autumn 

 pigments, would be mostly epiphasic between petroleum ether and 

 80 per cent alcohol, the normal xanthophyll solvent in the Kraus 

 separation. 



The difference between Miss Ooerrig's and Tswett's results respect- 

 ing water-soluble pigments can not be explained so readily, inasmuch 

 as the former proved that her leaf preparations from both green and 

 autumn leaves did yield strongly colored extracts to both distilled 

 water and to tap water, as well as to very dilute acetone. Leaf pow- 

 ders from leaves dried at 40 C. were used for these tests, while Tswett 

 examined only the fresh tissues. This difference alone may be suf- 



