1873.] Comparative Vegetable Chromatotogy. 463 



resisting the action o£ light and acids so well that they are very often 

 obtained as residues when all the colouring-matters of that group have 

 been decomposed. They, however, do ultimately fade. It is not yet cer- 

 tain whether these substances are essential for the growth even of lichens, 

 or only constant products. 



Orange Lichnoxanthine. 



This particular species occurs in many fungi, but I have more especially 

 studied it as obtained from lichens. Peltigera canina, growing well 

 exposed to the sun, should be crushed and heated in spirit. After 

 separating the whole of the chlorophyll in the manner already described, 

 the alcoholic solution should be evaporated to dryness, and the lichno- 

 xanthine and the phycoxanthine dissolved out by bisulphide of carbon. 

 On exposing this to the sun under green glass until the pink tinge is lost 

 and the absorption-bands of the phycoxanthine have disappeared, the 

 lichnoxanthine remains of an orange colour. Its spectrum, when the 

 solution is sufficiently strong, shows absorption of the whole of the blue 

 and green, gradually shading off to about the end of the yellow. The 

 modification soluble only in alcohol may be obtained from Platysma 

 glaucum and many other lichens by agitating the alcoholic solution with 

 bisulphide of carbon, and then diluting the alcohol with water, so that all 

 the substances soluble in the bisulphide may be carried down in it, all 

 soluble in water remain dissolved, and the modified orange lichnoxanthine 

 may be deposited in a free state, and, after separation, dissolved in ab- 

 solute alcohol. 



Lichnoxanthine. 



This is the most common member of the group, and is so widely dis- 

 tributed that it occurs in almost all plants, though sometimes in very 

 small quantity and not easily detected. It is best obtained from the yellow 

 fungus, Clavaria fusiformis. In the absence of that plant, it may be 

 prepared from the root of the carrot by dissolving out the colour in spirit, 

 and agitating with bisulphide of carbon to remove the orange xanthophyll 

 and the greater part of the xanthophyll. On evaporating the alcoholic 

 solution to dryness bisulphide of carbon dissolves the lichnoxanthine 

 along with a good deal of xanthophyll and yellow xanthophyll ; but by 

 exposing the solution to the sun, those two colouring-matters may be 

 destroyed, and the lichnoxanthine left alone. When pure and dissolved 

 in bisulphide of carbon it is of fine, somewhat orange-yellow colour, and 

 the spectrum shows a very uniform absorption, extending over the whole 

 of the blue, and ending suddenly about the centre of the green. It is 

 so difficult to separate this lichnoxanthine, properly so called, from orange 

 lichnoxanthine, that I shall frequently call the mixture the lichnoxanthines, 

 without attempting to give them alone. 



