1904.] KRAEMER — NATURE OF COLOR IN PLANTS. 263 



Plastid Color Substances. 



The green color in plants is due, as is well known by botanists, 

 to a green pigment known as chlorophyl which is associated with 

 a plastid or organized protoplasmic body, forming a so-called 

 chloroplast. Chlorophyl is distinguished from all other plant sub- 

 stances by possessing a dark broad band between the Fraunhofer 

 lines A and C at the red end of the spectrum, which is apparent 

 even in very dilute solutions. It also shows in more concentrated 

 solutions a broad band extending from F to the violet end of the 

 spectrum, a narrow band between C and D, or the orange portion 

 of the spectrum, and two narrow bands between D and E, or the 

 yellow portion of the spectrum. 



Pringsheim examined spectroscopically solutions of the yellow 

 substances found in etiolated germinating leaves, and also the 

 yellow substances of yellow flowers and autumn leaves, and 

 observed the characteristic chlorophyl bands only by using tubes 

 more than three hundred millimeters thick. Inasmuch as small 

 tubes holding five or ten cubic centimeters are sufficient for the 

 examination of chlorophyl, by means of the Zeiss or Leitz micro- 

 spectroscope, and also because a dilute solution is necessary, one 

 is surprised that Pringsheim and others have used tubes of such 

 enormous thickness, and that they concluded from the more or less 

 indistinct bands which they observed that these substances were 

 modifications of chlorophyl. It is not at all unlikely that what 

 he actually had were concentrated solutions of as many different 

 principles, each of which contained traces of chlorophyl, notwith- 

 standing the care he exercised in separating the green and yellow 

 portions in the material which he used. 



In my own studies on the yellow principle of developing leaves 

 I used the buds of skunk cabbage, which develop under ground and 

 under leaves and are of considerable size before exposed to light. 

 The outer light greenish-yellow portions were removed, and only 

 the intense yellow central portion used. This material was 

 extracted in the dark with alcohol. The solution thus obtained is 

 of a pure lemon-yellow color, and may be freed from cell-sap sub- 

 stances either by evaporation to an extract, washing with water, 

 dissolving in cold alcohol, and then boiling with zinc ; or by treat- 

 ing the original alcoholic solution with petroleum benzin, whereby 

 the pure yellow leaf substance is separated from the cell-sap substance. 



