Comparative Stitdy of Chloi'ophyll. 411 



Kraus' band Y., and the sixth to Kraus' band VI. I have 

 not been able to see tne band in the green part of the 

 spectrum or Kraus' band IV, ; but I have proved that Kraus' 

 band I. really consists of two bands, and accordingly I have 

 drawn in spectrum 11, Plate IL, what I consider to be the 

 correct absorption-spectrum of chlorophyll. It will be seen 

 from this figure that the darkest band in the spectrum is my 

 band No. 1 ; then come in succession band No. 5, bands 

 No, 6 and No. 2, band No. 4, and ultimately band No. 3. 

 It is evident, therefore, that band No. 3 is paler and 

 narrower than No. 4 in living chlorophyll, while in alcoholic 

 and xylol extracts the reverse is the case. This is difficult 

 to explain ; it may be that the extractive acts on the normal 

 chlorophyll, producing this change, or that the fourth band 

 becomes more evident when once removed from tissues, or 

 that the spectrum of chlorophyll is the spectrum not of 

 " one " body, but of several bodies, which are extracted in 

 varying amounts according to the nature of the extractive. 



I shall proceed now to compare the absorption-spectrum 

 of living chlorophyll with the absorption-spectra of extracts 

 made in various ways. 



The two first bands (Kraus' band I.), which, in a mode- 

 rately strong alcoholic extract of fresh material (spectrum 2) 

 extend from \ 678 — X 628, occupy, in an extract made 

 from material which has been boiled for ten minutes, a 

 position between X 690 — X 635 (spectrum 5). The two 

 bands are darker in colour, and shifted also slightly towards 

 the red end of the spectrum. The addition of three drops 

 of liquor ammonii to a test-tube full of an extract made 

 from boiled material will cause Kraus' band I. to become 

 lighter towards the blue end of the spectrum, and in addition 

 it will form a new band to the left of Kraus' band I., the 

 centre of this new baud being about X 706 (spectrum 6). This 

 peculiar action of a strong caustic was first described by F. 

 Chautard.* 



While thus the addition of an alkali causes the appear- 

 ance of a new band to the left of what is normally the first 

 band, an acid seems to have the reverse action, for it renders 

 the spectrum to the left of the Fraunhofer line B brighter, 

 and it shifts the position of the left margin of the first band 



* Comptes Rendiis, torn. Ixxvi. 570. 



