Comparative Studi/ of CJilorophyll. 399 



widening out and fusing with the second band, which 

 itself becomes darker ; and if, secondly, not too much light 

 is used, or the pale second band will be " liooded " with 

 light, and will be invisible. 



This second band is most evident if an Argand burner be 

 used as the source of light ; and also when working with 

 cryptogamic and phanerogamic plants I find it best to use 

 the Argand burner, as the Fraunhofer lines in the red end 

 of the spectrum are very apt to mislead in the calculation of 

 the absorption-bands. I may mention further that, although 

 many authorities who have been working at chlorophyll state 

 that the bands in the blue end of the spectrum can only be 

 seen in sunlight, it is not only possible to see them in artificial 

 light, but to me at least they are as evident as in sunlight, 

 if not more so. 



Whether it is possible to see Kraus' bands II. and III. 

 in Spirogyra when examined as above stated I cannot 

 definitely say; but sometimes when working with very 

 thick layers I believe I have seen an absorption in the 

 yellow orange, but I am not able to prepare material to 

 demonstrate the bands beyond all doubt. 



The absorption in the blue end of the spectrum with its 

 centre, about X 485, is evident enough ; but the second 

 absorption, with its centre about X 450, is very difficult to 

 make out. 



I next proceeded to make an alcoholic extract in the 

 following manner : — Spirogyra, in as healthy a condition as 

 possible, was carefully washed in distilled water to remove 

 all impurities, organic and inorganic, which might be 

 clinging to the threads, and then placed on filter paper in a 

 thoroughly cleaned glass funnel ; and after five minutes, when 

 most of the water had run off, it was placed by means of a 

 glass rod into another funnel and pressed down firmly, without 

 injuring the threads, however, and absolute alcohol was poured 

 slowly over the mass ; after two to three miniites a good 

 deal of the colouring-matter was extracted, and then the 

 absolute alcohol, which had been collected in a wide test- 

 tube, was filtered twice and examined at once. The whole 

 process occupied about ten to fifteen minutes after washing 

 the material in distilled water, and was conducted in a room 

 with just sufficient light to allow me to see what I was doing. 



