accompanying Chlorophyll and their Spectroscopic Relations. 475 



a band in the red being due to a trace of chlorophyll that has not been 

 removed, but in some instances depending upon the particular plant 

 experimented with, and the same plant at different seasons, The fourth 

 and most refrangible band is extremely faint, if not absent (Plate 6, 

 F, 1). This variation of the spectrum I failed to observe in my former 

 experiments, and its significance will be apparent later on. As pointed 

 out in my former investigation,* in some instances only the first two 

 or three bands are visible, the rest of the violet and ultra-violet being 

 obscured by a yellow colouring matter producing general absorption, 

 but no bands, which, according to Sorby, belongs to his Lichnoxanthine 

 group, and corresponds to the so-called xanthophyll of Tschirch. In 

 such cases a separation can be effected by agitating with ether, and the 

 addition of water, the colouring matter causing the obscuration 

 remaining in the watery alcoholic solution. In every case the extent 

 of the ultra-violet visible varies, depending, as before, upon the par- 

 ticular plant experimented upon and the same plant at different 

 seasons. 



Most of the present experiments were made with alcoholic extracts 

 obtained from Ficus Carica and Ficus Piepens, both of which give a very 

 excellent chlorophyll spectrum, pointing to the presence of very little 

 acid in the juices of the leaf, and, as the presence of acid affects the 

 xanthophylls, it is of importance to prevent complications to experi- 

 ment with a plant that is more or less free from acid in its juices, a 

 delicate indication of which is the condition of the chlorophyll spec- 

 trum of the alcoholic extract, whether normal or not, for the least 

 trace of acid will cause the fourth chlorophyll band to become pro- 

 nounced instead of appearing very faint. The observations of the 

 absorption spectra were effected as before by means of photography, 

 quartz lenses and an Iceland spar prism being used, and the source of 

 light was a Welsbach incandescent gas mantle of 60-candle power. 



The method of procedure was to agitate the crude alcoholic solution 

 of the xanthophylls from which the chlorophyll had been removed by 

 one of the above means with successive equal volumes of CS 2 until no 

 more colouring matter was taken up by the CS 2 , each volume of CS. 2 

 being equal to about half the volume of the crude solution experi- 

 mented upon. By this means we have the colouring matters capable of 

 being taken up by CS 2 divided into several CS 2 portions or fractions 

 (which varied from six to twelve according to the concentration of the 

 crude solution) according to their relative solubility, leaving in the 

 alcohol those colouring matters which are more soluble in it than 

 in CS 2 . 



On examining first the alcoholic portion from which the dissolved 

 CS 2 had been evaporated by gentle heat, it is found to be a paler 

 yellow than the crude solution and to give four absorption bands in 

 '* ' Roy. Soc. Proc./ vol. 65, p. 181. 



