3o8 PIGMENTS 



of water to the dry solvent dissolves some of the salts present 

 in the dry leaf material and these precipitate the chlorophyll 

 which is then taken up by the solvent. On treating leaves 

 with boiling water, chlorophyll diffuses from the chloroplasts 

 and the spectrum shows a lateral displacement towards the 

 violet, the absorption bands being almost coincident with 

 those of a true solution in phytol. Willstatter and Stoll 

 explain this on the assumption that the hot water brings 

 about a change in the sol condition, thus the wax-like sub- 

 stances present in the cell, which are liquefied at the tempera- 

 ture of boihng water, dissolve the chlorophyll, making a true 

 solution. For these reasons Willstatter and Stoll conclude 

 that the chlorophyll in the leaf is in a colloidal solution. 



It will be remembered that solutions of chlorophyll are 

 marked by a strong fluorescence, which property is exhibited 

 only in true solutions, not in colloidal solutions ; wherefore, 

 if a preparation of chlorophyll or the chlorophyll in the living 

 cell shows fluorescence, it should be in true solution. Using 

 a culture of Chlorella, Stern * found that the position of the 

 fluorescent band closely agreed with that of a solution of 

 chlorophyll in lecithin. This lipoidal sol, compared with an 

 alcoholic solution, shows a lateral displacement of the spec- 

 trum towards the red, a displacement due to the difference in 

 the refractive indices of the two solvents. Stern further ob- 

 served that a chlorophyll sol, shaken up with protein, sugar or 

 glycerol, exhibits no fluorescence ; but when shaken up with 

 oil, soap, lecithin and other phytosterols, fluorescence obtains 

 owing to the solution of the chlorophyll in the fatty material. 

 He concludes that in the living cell chlorophyll is in true 

 solution in a lipoid medium dispersed in an aqueous protein 

 phase. 



With regard to the distribution of the pigment within 

 the plastid there is again some dispute. According to many, 

 it is distributed evenly throughout the stroma, whilst, on the 

 other hand, others maintain that it is restricted to the periph- 

 eral layers of the plastid. 



* Stern : " Ber. deut. bot. Gesells.." 1920, 38, 28 ; " Zeit. Bot.," 192 1 

 I3> 193- 



