July 15, 191S Heredity of Color in Phlox Drummondii 295 



PLASTID COIvOR SUBSTANCES 



There are found in most plant cells lying in the cytoplasm outside of the 

 nucleus small bodies called "chromatophores." In embryonic cells and 

 growing points these chromatophores are colorless and highly refractive, 

 and this condition may be retained until the cells reach maturity. Ordi- 

 narily, however, these colorless chromatophores attain a further develop- 

 ment as chloroplasts, leucoplasts, or chromoplasts. 



CHLOROPLASTS 



In parts of the plant which are exposed to the light, the chromatophores 

 usually develop into chlorophyll bodies of flattened ellipsoidal shape and 

 are scattered in numbers in the parietal cytoplasm of the cells. These 

 granules contain two pigments, green and yellow, the former predominat- 

 ing often to the complete exclusion of the latter. The yellow pigments 

 of the chloroplasts are collectively termed ' ' xanthophyll . ' ' The green and 

 yellow pigments may be separated from each other, aod each can be 

 readily seen by placing green leaves, which have been previously boiled 

 in water, in alcohol and adding benzol. When this solution is shaken 

 and then allowed to stand, the benzol will rise to the surface as a green 

 solution, leaving the alcohol yellow. 



CHROMOPLASTS 



The chromoplasts of most flowers and fruits arise either directly from 

 the rudiments of colorless chromatophores or from previously formed 

 chloroplasts. The color of the chromoplasts varies from yellow to red, 

 according to the predominance of yellow xanthophyll or orange-red 

 carotin. The name "carotin" has been derived from the carrot (Daiicus 

 carota), in the roots of which it is particularly abundant. Carotin is 

 practically identical with the so-called "chrysophyll" found in the 

 chloroplasts. 



It will be seen that there is a very close relationship between the 

 chloroplasts and chromoplasts and the green and yellow colors found 

 in them. In general, however, it may be said that the yellow color in 

 certain roots, flowers, and fruits is due to the yellow pigments of the 

 chromatophores. 



CElvL-SAP COLOR SUBSTANCES 



During the process of metabolism the plant cell manufactures other 

 color substances which are not combined with the protoplasm, but which 

 are contained in the cell sap, or liquid of the cell. These substances, 

 unlike other plastid colors, are insoluble in xylol, ether, or similar sol- 

 vents, but are soluble in water and alcohol, which aff"ord a means of 

 separating them from the plastid colors. These cell-sap pigments may 



