1873.] Comparative Vegetable Chromatology . 457 



rather obscure ; but a further study o£ it seems likely to throw light ou 

 the cause of the production of some of the colouring-matters found in 

 particular plants. When such a sensitizing substance is absent, so that 

 the alteration takes place too slowly, a little turpentine is an excellent 

 substitute. The changes which occur vary according to the particular 

 species of the group, and thus furnish a valuable means for distin- 

 guishing them, or for recognizing small quantities of some when mixed 

 with others. 



PhycoxantJiine. 



This name was first proposed by Kraus* for a substance he obtained 

 from Oscillatorice ; but there is no doubt whatever that his preparation 

 was a mixture of two or three distinct kinds of colouring-matters, which 

 can easily be separated, and do occur separately in other plants. That 

 for which I adopt the name may be obtained in the most pure state from 

 the lichen Peltigera canina when growing in a very damp and shady 

 place, or from some species of Oscillatorice when growing quite open to 

 the sun. The various coloured substances should be dissolved out by 

 hot spirit, and the solution when cold diluted, if requisite, with a little 

 water, and agitated over and over again with fresh quantities of bisul- 

 phide of carbon until it subsides tinged only a pale pink. By this 

 means almost the whole of the other colouring-matters are carried down, 

 with the exception of the lichnoxanthines. On evaporating the alco- 

 holic solution and redis solving in bisulphide of carbon, a red solution is 

 obtained, which, when more dilute, is a fine pink, and gives a spectrum 

 with two excellent absorption-bands in the green. When it is dissolved 

 in absolute alcohol these bands lie much further from the red end, and 

 the colour is sufficiently } r ellow to justify the name phycoxanihine, or, at 

 all events, to make it undesirable to introduce another. On adding a 

 little hydrochloric acid and turpentine, the colour gradually fades, with- 

 out the production of any well-marked intermediate coloured substance. 

 I am much inclined to believe that this phycoxanthine may be formed 

 from orange xanthophyll, both artificially and naturally ; but since this 

 change occurs only in very rare and special cases, it probably depends 

 on the presence of some sensitizing substance, only occasionally present 

 or under conditions not yet understood. 



Peziza Xanthine. 



This is the name I propose for an orange-yellow colouring-matter 

 found in Peziza aurantia and some other fungi. It resembles phyco- 

 xanthine in many particulars, but differs in the position of the absorption- 

 bands, which lie further from the red end. 



Orange Xanthophyll. 

 This is one of the most universally distributed of all vegetable eolour- 

 * Chlorophyllfarbstoffe, p. 109. 



