1899] COLOURING MATTERS OF FLOWERS 145 



vertes et colorees," in which he, with great acuteness, insisted that the 

 red and blue colouring matters of plants are not formed from chloro- 

 phyll ; and the blue colouring matter (anthocyan) is probably, like 

 litmus, the alkali salt of an acid which in the free state constitutes the 

 soluble red pigment (erythrophyll) of autumn leaves. It will be noticed 

 also that Morot had clearly enounced that a red colour could possibly 

 be formed independently in the leaf, in fact it is seen to be produced 

 without having previously passed through a blue tint ; in other words, 

 it was not derived from the blue. Here, then, there was a farther 

 break up of the olden entanglement, for not only were the blue and 

 red separated from the green, but the red was threatened with divorce 

 from the blue. Now, it was just precisely at this critical point in the 

 scientific enlightenment of the mystery that two papers were published 

 which may rank among the more interesting efforts of an epoch fertile 

 in important researches and discoveries. 



In the Botanische Zeitung, dated April 18, 1862, there appeared 

 an article entitled " Some Propositions anent the Physiological Meaning 

 of Tannin and of the Pigments of Plants " by A. Wigand, in which the 

 author, after giving various illustrations, and leaving chlorophyll, an- 

 thoxanthin, indigo, etc., out of account, avers that "in general it results 

 from the foregoing as to nearly all blue and red pigments that these 

 proceed from tannin through an only unessential modification." . . . 

 ' A colourless substance dissolved in the cell sap furnishes the basis 

 for anthocyan, and this chromogen is tannin, or rather some modifica- 

 tion of tannin (cyaneogen) : the transformation of cyaneogen into 

 anthocyan depends on an oxidation." Again, early in I860 Professor 

 W. Stein suggested that the red colouring matter of flowers was para- 

 carthamin, a red substance which he had obtained by the action of 

 sodium amalgam on the plant-yellow (rutin) that had been discovered 

 by Weiss in 1842. 



" Notwithstanding the extreme suggestiveness of the declarations 

 just now set forth, appealing as they did most forcibly to the scientific 

 intelligence, it is extremely discreditable that, so far as concerns 

 Germany, they were practically ignored for nearly twenty years. No 

 doubt Wiesner, alluding to Wigand's paper, had published some observa- 

 tions about eight months afterwards, and again in 1872; and Kraus, 

 in 1872, had connected the red coloration of winter leaves with the 

 presence of tannin. But it was not till 1881 that Detmer confirmed 

 the views of Kraus, and H. Pick, in 1883, by an elaborate histological 

 and micro-chemical investigation of young shoots, older stems, petioles, 

 fruits and their peduncles, and autumn leaves, fully and amply ex- 

 tended and ratified the propositions enunciated with such brilliant 

 genius by A. Wigand. " We now," he states, " on the basis of our 

 researches, assert with Wigand, as a fact, that the red pigment is to be 

 found only in plants containing tannin, and that the tannin, at first colour- 

 less, can change into the red pigment, which likewise reacts like tannin." 



