Studies on color in plants* 



Henry KraexMer 



The subject of color may be viewed in a number of ways. 

 The physicist considers colored substances in their relation to 

 light, and defines color as due to the influence which the substance 

 has upon the vibration of the ether-waves and as dependent upon 

 physical conditions. The chemist is interested in the constitution 

 and composition of the colored substance, while the biologist is 

 concerned with its origin and the role which it plays in metabolism 

 or the life-processes of the plant or animal. The nature of color 

 in plants and animals is more or less distinct, and while a number 

 of animal pigments have been isolated, as cochineal and lac-dye, 

 the color effects in animals are due largely, especially in the 

 plumage of birds, to physical structure, i. e. y light interference 

 phenomena or the dispersion of light rays. While structural 

 arrangement in plants has also an influence on the color effects, 

 still the colors in plants are usually looked upon as being due to 

 distinct chemical principles without special reference to physical 

 structure. 



Upon making a section of some colored tissue of the plant, we 

 find cells containing two or more of the following substances. In 

 the first place there is in the living cell a semi-fluid, viscous, gran- 

 ular or foam -like substance known as protoplasm, of which, as 

 regards its chemical composition and function, we know little more 

 than when it was first described by von Mohl in 1 846. This lies 

 either close to the walls of the cell, forming a relatively thin layer 

 or lining, which encloses a large vacuole of cell-sap, or it may be 

 distributed in a mesh-work, forming smaller vacuoles. Within the 

 protoplasmic mass we find a differentiated body known as the 

 nucleus, and in recent years much of the work done by biologists 

 has been devoted to a study of this body. There are in addition 

 other protoplasmic bodies found in the plant cell, known as plasties, 



* Read before the Torrey Botanical Club, with illustrations and demonstrations, 

 December 12, 1905. More complete details of the work will be given in future issues 



of this Bulletin. 



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