412 Mr Gustav Mann on the 



towards the right side, as will be seen by comparing spectra 

 6 and 7, the left margin in fig. 6 equalling X 690, while in 

 spectrum 7 it corresponds to X 682. 



In extracts made with benzol and xylol the extent of the 

 two first bands corresponds almost to that of living chloro- 

 phyll, for in Sjnrogyra the two first bands collectively equal 

 X 678 — X 638 in living chlorophyll, while the bands measure 

 in benzol and xylol on an average X 675 — X 633*5. 



Spectra 8 and 9 will show also that Kraus' band I. is 

 the result of the fusion of the darker left band with the 

 paler right one. 



I may just mention that Schunck * has drawn in spectrum 

 2, representing a very dilute alcoholic extract, a band 

 corresponding very nearly to my first band. 



As to bands 3 and 4 (Kraus' bands II. and III.) I have 

 already stated that in living chlorophyll band 4 is darker 

 than band 3, while the reverse holds good for extracts. 



As to the absorption-band in the green part of the 

 spectrum, namely, Kraus' band IV., I must say that I have 

 not been able to make out the slightest absorption when 

 working with living chlorophyll ; Tschirch "j" figures Kraus' 

 band IV. amongst his absorption-bands of living chlorophyll. 

 According to his statements, it becomes visible if four or 

 more leaves are examined at once, but as neither the name 

 of the plant nor the method of examination are described, I 

 was unable to repeat his experiments. The fourth band of 

 Kraus can therefore either not be demonstrated by the 

 methods I employed, or it does not exist in normal living 

 chlorophyll. 



Schunck notices that the band in the green, according to 

 some authors, is very faint, while, according to others, it is 

 considerably darker than the band in the yellow ; and he is 

 of the opinion that the band in perfectly pure chlorophyll 

 would be absent. By referring to my figure 3, a band in 

 the green part of the spectrum will be noticed, but the layer 

 of extract used was sufficiently thick to cause fusion of the 

 first three bands of Kraus into one absorption. This 

 extract was made according to my method, as fully stated 

 above. If we compare spectrum 3 with spectrum 5 we find 



* "Chemistry of Chlorophyll," Annals of Botany, vol. iii. No. ix. 

 + Berichtc der Dcutschcn Botan. Ocsellsch. , Band i. 



