IO 



PHYSIOLOGY OF NUTRITION 



cording to their intensities, they form the series: I, VI, V, II, III, IV. The 

 first band, lying between the Fraunhofer lines B and C, is the most distinct; it 

 appears in solutions of weaker concentration than are necessary to make the 

 others evident. The absorption bands become broader with increasing con- 

 centration and finally merge into one another, so that only the red rays, between 

 A and B, and a part of the green can pass through a concentrated solution or a 

 thick layer; finally, with still further increase in concentration or thickness 

 of layer, the green rays are also completely absorbed and only the rays between 

 A and B are transmitted. All objects appear red when seen through a very 

 concentrated solution or a very thick layer. 



a£ C 



7& 70 «J 



Fig. 4. — Absorption spectrum of ethyl chlorophyllide, 0.1 g. in 5 1. of alcohol. {After 

 Willstatter.) The thickness of the layer employed is shown (in millimeters) at the left, the 

 conventional letters of the Fraunhofer lines are at the top, and the wave-lengths (in 10 nn) 

 are indicated below. 



The absorption spectra of chlorophyll a and chlorophyll b, in acetone, are 

 shown in Figs. 5 and 6, reproduced photographically, these being taken from 

 Willstatter and Stoll's monograph (Tafel VIII). Five different concentrations 

 are employed, the strongest being represented by the lowest spectrum in each 

 case. The Fraunhofer lines and wave-lengths (in /jl/j.) are shown above/ 



The spectrum of living leaves shows the same absorption bands as does the 

 spectrum of an alcoholic solution of chlorophyll (ethyl chlorophyllide); in the 

 former case the bands are merely displaced a little toward the infra-red end of 

 the spectrum. ° 



The researches of Schunck and Marchlewski 1 have contributed much to an 

 understanding of the chemical character of chlorophyll. The action of hydro- 



1 Schunk, E., and Marchlewski, L., Zur Chemie des Chlorophylls. Liebig's Ann. Chem. u. Pharm. 

 278: 329-345. 1894- 



s These two figures are added by the editor. — Ed. 



B It seems highly probable that the chlorophyll of living leaves exists in colloidal solution. 

 (Herlitzka, A., Neben den Zustand des Chlorophylls in der Pflanze und iiber kolloidales 

 Chlorophyll. Biochem. Zeitsch. 38 : 321-330. 1912. Iwanowski [D.], Ueber das Verhalten 

 des lebenden Chlorophylls zum Lichte, Ber. Deutsch. Bot. ges. 31 : 600-612. 1913). — Ed. 



