CHLOROPHYLL AND THE CHLOROP LASTS 351 



tion to remove red and yellow rays, onto the material containing the 

 chlorophyll. In this manner, the blood-red fluorescent rays can be de- 

 tected even in extremely dilute chlorophyll solutions. Tswett ''' states 

 that he was able to detect methylphaeophorbid a in a concentration of 

 1 : 100,000,000 in his luminoscope. 



The fluorescence of plants containing chlorophyll has also been studied 

 by microscopic methods. Thus Tswett made use of the Reichert fluores- 

 cence microscope. As a source of light he used rays of X < 450 \i\i. In 

 Spirogyra and Elodea he observed two lines in the fluorescent light : \ = 

 685-670 and X = 660-650. The first line he considers is due to chloro- 

 phyll a while the second line, which is weaker than the first, is probably 

 due to chlorophyll b. The fluorescence has also been observed in the ultra- 

 microscope by Wilschke,-* Giklhorn -^ and by Gaidukow.-° 



Lloyd ^^ has devised methods of demonstrating the fluorescence of 

 chlorophyll and other pigments microscopically by means of the dark field 

 illuminator of wide aperture. He found that when blue green algae are 

 heated enough to destroy the water soluble phycocyanin, the chlorophyll 

 is unmasked and the fluorescence thereof may be seen with the micro- 

 spectroscope, using appropriate filters to remove the red to green rays from 

 the source of illumination. Lloyd gives the fluorescent rays as ^ = 650- 

 700 \i\i. He has made preparations of a large number of plants by this 

 method. By using solutions of cane sugar or glycerine, which cause the 

 cells to collapse, he was able to demonstrate the fluorescence of algae and 

 higher plants. An interesting point noted by Lloyd is that on heat- 

 ing Spirogyra to the boiling point of water, "the chlorophyll is not ren- 

 dered non-fluorescent, but it becomes more or less extruded into vacuoles 

 which originate in the chloroplast, and these now contain the chlorophyll, 

 or at least a derivative of it. which can be seen to be fluorescent without 

 the aid of filters." 



It will be recalled that Willstatter and Stoll prepared colloidal solu- 

 tions of chlorophyll in water and found that these were non-fluorescent. 

 Nevertheless, on account of the similarity in the position of the absorption 

 bands between colloidal chlorophyll solutions and living leaves, they and 

 Herlitzka were inclined to believe that in the living leaf the chlorophyll 

 was in a colloidal state. It was found that leaves which had been im- 

 mersed in boiling water had an absorption spectrum analogous to true 

 chlorophyll solutions, and from this fact, it was concluded that the chloro- 

 phyll in such leaves, was no longer in colloidal solution. It is evident, 

 however, that the observation of Lloyd just mentioned is not in entire 

 accord with this conclusion. 



Stem 28 bases his conclusion, that chlorophyll is not in a colloidal state 



"Tswett, Ber. hot. Gcs., 29, 744 (1911) ; Zcit. physik. Chan., 36, 450 (1901). 



"Wilschke, Zcit. zmss. Mikros., 31, 338 (1914). 



"Giklhorn, Sitsmigsb. Akad. Wiss. Wicn. Math.-nat. Kl. Abt. 1, 123, 1221 (1914). 



"Gaidukow, "Dunkelfeldbeleuchtung," Jena, 1910. 



"Lloyd, Science, 58, 91, 229 (1923) ; 59, 241 (1924). 



» Stern, Ber. bot. Ges., 38, 281 (1920); Zeit. Bot., 13, 193 (1921). 



