CHAPTER II. 



Certain yellows evidently are the product of a i)receding 

 chlorophyl green. Chemists inform us that the coloring of 

 chlorophyl is composed mainly of yellow and blue pig- 

 ments, which can readily l)e separated. 



This process takes place naturally in leaf and petal, the 

 l)lue portion ))eing absorbed by the plant, or in some other 

 manner eliminated, while the yellow element remains. This 

 may be illustrated by the Chinese primrose, which, of what- 

 ever hue, has a central green eye. This green spot often 

 remains unchanged, but usually it becomes moditied, in 

 color varying from yellowish green to pure yellow, the 

 yellow color being confined strictly to the space previously 

 occupied l)y the green. It is obvious therefore that this 

 particular yellow was occasioned by the decomposition of 

 the chlorophyl. The same is true in most cases of both 

 green petals and green leaves, viz., that the yellow depends 

 for its existence upon a previous green color. If one ob- 

 serves the ripening leaf, even before there is any frost, say 

 as early as the middle of August, he will tind that some of 

 those of Rhus copalinu, for instance, have become already of 

 a yellow color, other leaves on the same bush will be scarlet, * 

 while others still may be partly yellow and partly scarlet. 

 A similar color change is seen in maples, Crofon, Coleus, 

 AcJiijvantJtes and in green petaled liowers. Which color 

 ought one to i)ron()unce the most primitive? According to 

 Prof. Vines, "the green and the yellow coloring matters of 

 |)Iants are deposited in corpuscles of a protoplasmic nature, 

 but the others, especially the red and l)lue, are dissolved in 

 the cell sap. It is to the presence of coloring matters in 

 solution in the cell sa[) that the colors of petals are princi- 

 pally due." The red and blue colors then are quite inde- 

 pendent of the yellow. They may develop before the 



