Kraemer: Color in plants 79 



The plastid pigments are distinguished from all other color- 

 substances in the plant by the fact that they are insoluble in water 

 and soluble in ether, chloroform and similar solvents. This 

 seems to be a wise provision, as it probably prevents the diffusion 

 of these principles in the more or less aqueous cell-sap. These 

 plastid pigments are but little affected by the usual chemical re- 

 agents under ordinary conditions. 



Apart from the difference in color, the yellow pigment is dis- 

 tinguished from the green by the fact that the latter is said to 

 contain nitrogen, and also by their difference in behavior when 

 examined spectroscopically, chlorophyl giving several distinct 

 bands in the yellow and orange portion of the spectrum, which 

 are wanting in the spectrum of the yellow principle. 



The leaf-buds of the skunk cabbage are quite large, consisting 

 of numerous leaves. The innermost leaves are of a distinct yellow 

 color. A microscopical examination of these shows that the color 

 is due to a plastid which is very much smaller than the chloro- 

 plastids or chromoplastids found in the fully developed leaves and 

 flowers of the plant. This plastid occurs in the palisade cells and 

 contains neither starch nor proteid substances, and the yellow pig- 

 ment appears to be somewhat similar to that found in chromoplastids, 

 but differs in this, that on reducing with zinc it becomes slightly 

 greenish. This plastid, which I have provisionally termed an 

 etioplastid (and the pigment etiophyl), appears later, with the devel- 

 opment of the leaf, to be transformed into a chloroplastid, whereas 

 just the reverse takes place with chromoplastids, that is, they may 

 be derived from chloroplastids. I may further say with regard to 

 the pigment etiophyl, that on purification and treatment with zinc 

 it appears to be entirely distinct from chlorophyl when viewed 

 both by transmitted and reflected light and when examined by 

 means of the spectroscope. It is also characterized by its greater 

 stability even when exposed to light, and may be partly separated 

 from chlorophyl in an alcoholic solution (85 per cent, alcohol) by 

 means of benzin. An interesting observation which I have made 

 in this connection is that when leaves of skunk cabbage containing 

 both etiophyl and chlorophyl are extracted with alcohol, purified, 

 and reduced with zinc, the resulting solution is a deep green and 

 retains this color. 



