NUTRITION 53 



made to isolate chlorophyll none has yet been really suc- 

 cessful. * 



The fluorescent quality of chlorophyll, more evident in 

 its solutions than in the leaf, is revealed by the blood-red 

 color visible when light is reflected from it. However, the 

 physiological significance of this fluorescence is not under- 

 stood. 



The spectrum of a fresh alcoholic solution of chlorophyll 

 is essentially the same as that of chlorophyll in the unin- 

 jured leaf. The spectra vary in any case with the density 

 of the solution, the thickness of the layer through which the 

 light passes, whether of solution or of uninjured tissue, and 

 also with the plants examined. The different shades of 

 green leaves similarly exposed to light, the differences in 

 their spectra, and in the spectra of solutions derived from 

 them, and the different substances obtained in the chemical 

 examination of chlorophyll solutions from different species 

 of plants, all point to there being at least different propor- 

 tions of the component pigments of the mixture called 

 chlorophyll, if not different pigments in the chlorophyll of 

 different plants. Though the function of chlorophyll the 

 absorption of energy in the form of light rays is the same 

 in all green plants, it by no means follows that the chloro- 

 phyll of all plants is equally efficient in absorbing light rays 

 or that exactly the same rays are used in all plants. Slight 

 differences in the composition of chlorophyll would cause 

 corresponding differences in the quality and in the quantity 

 of the energy absorbed by it. 



The spectra obtained from light which has passed through 

 a leaf, and of alcoholic solutions of chlorophyll, are char- 

 acterized by dark bands called " absorption bands," the 

 broadest and darkest of which are between the lines B and 

 C, and E and F, of the normal solar spectrum, that is, in 



* The literature of the subject is voluminous. References to the older 

 literature may be found in Monteverde's papers ( Acta Horti Petropolitani, 

 t. XIII. . 1893) ; Kohl's (Bot. Centralbl., Bd. 73 et seq., 1898) ; Bode's 

 (ibid., Bd. 77, 1899), and in an extended paper promised by Tswett, in 

 his preliminary announcement in Bot. Centralbl. Bd. 81. 1900, also in a 

 collective review by Czapek in Bot. Zeitung. II. Abth.. May, 1900. 



