I^J^ 



PROCEEDINGS 



or THE 



AMERICAN PHILOSOPHICAL SOCIETY 



HELD AT PHILADELPHIA 

 FOR PROMOTING USEFUL KNOWLEDGE 



Vol. XLIII. April-September, 1904. No. 177. 



THE ORIGIN AND NATURE OF COLOR IN PLANTS. 



BY HENRY KRAEMER. 



(Read April 8, 1904.) 



A list of the more important papers published, up until within 

 the past ten years, on the subject of plant colors is given in 

 Dippel's Das Mikroskop. ^ Of these the papers by Pringsheim^ 

 on the examination of chlorophyl and related substances, and by 

 Miiller ^ on the spectrum-analysis of the color substances of flowers, 

 are probably the most important. 



Pringsheim confined his attention mainly to a spectroscopic 

 study of chlorophyl and the yellow substances in germinating 

 plants, yellow flowers and yellow autumn leaves. He concluded 

 that the yellow substances from these several sources were but 

 modifications of chlorophyl. The yellow principle found in ger- 

 minating plants he regarded as closely related to chlorophyl, and 

 the yellow substance in autumn leaves as a more remote modifica- 

 tion of it. He did not consider, however, as subsequent writers 

 have claimed, that these substances were identical. 



Two years before the appearance of Pringsheim's paper, Kraus^ 

 stated that he had separated from an alcoholic solution of chloro- 

 phyl by means of benzol two distinct substances, one yellow and 

 the other blue, the latter being taken up by the benzol. Pring- 

 sheim, however, showed that the blue substance was in reality 

 chlorophyl, and that the alcoholic solution, which showed faint 

 chlorophyl-like bands in the spectroscope, still contained some 

 chlorophyl. 



PROC. AMER. PHILOS. SOC. XLIII. 177. Q. PRINTED JULY 27, 1904 



