600 SCIENCE PROGRESS 



mode of formation of the anthocyan pigments in plants. He 

 further confirmed the presence of the yellow pigments, for which 

 he used the name XantheTn (cf. Fremy and Cloez) in anthocyan- 

 containing flowers, and as the result of his work was led to put 

 forward the hypothesis that both yellow and red pigments have 

 their origin in a faintly yellow substance produced in the sap of 

 all plants, and which by oxidation, particularly under the in- 

 fluence of alkalies and light, produces the different yellow pig- 

 ments, from which, by further action of light and oxygen, the 

 red pigments are produced. It is interesting to note that the re- 

 lationship thus suggested by Martens as existing between the 

 yellow pigments and the anthocyans is that which has been 

 revived in more recent years by Wheldale ; Keeble, Armstrong, 

 and Jones, and others (see below). 



In 1859, Morren put forward the suggestion that the blue 

 flower pigments (anthocyans) were the alkali salts of acids 

 which in the free state are red, and for which he uses the name 

 Erythrophyll (cf. Berzelius). His conception of the blue pig- 

 ments has been confirmed by recent work, but not so that of 

 the red colouring matters. 



A number of workers have, at different times, attempted to 

 prepare pure anthocyan pigments by making use of the lead 

 salts (cf. Berzelius), thus Glenard (jCompt. rend. 47, 268 ; Jahrber. 

 1858, 476), working with red wine, and using ethereal hydro- 

 chloric acid for the decomposition of his lead salt, obtained a 

 pigment which he called cenolin, and for which he put forward 

 the nitrogen-free formula C 20 H 16 Oio. His pigment was, how- 

 ever, by no means pure. Senier (cf. Jahresber. 1878, 970), using 

 rosa gallica, and decomposing his lead compound, suspended 

 in alcohol, either by sulphuric acid or sulphuretted hydrogen, 

 prepared a pigment, for the lead salt of which he gave the 

 formula C 21 H 29 O 30 Pb 2 . Heise (cf. Chem. Centralblatt, 1889, 2, 

 953). by similar means, prepared two pigments (A and B) from red 

 wine, using sulphuretted hydrogen for decomposing the lead 

 salt, and suggested that Glenard's compound was a mixture of 

 these. His examination of these products was not complete. 

 Glan {Dissertation, Erlangen, 1892), examining the pigment of 

 the deep-red hollyhock, also obtained two products, and in 

 1894, Heise (cf. Chem. Centrblt. 1894, 2, 846) further prepared 

 two pigments (A and B) from the bilberry (in this case using 

 ethereal hydrochloric acid to decompose the lead salt), and ob- 



