ANTH.OCYANIN AND SUGAR 253 



Other aquatic plants behave similarly, but in the case of 

 cut shoots of lilies the red pigment only developed provided 

 sugar were added to the culture solution. 



Further experiments showed that the' red colour is not 

 formed in those plants, in which the pigment was restricted to 

 the epidermis, when cultivated in sugar solution. Success only 

 resulted in those cases where the colouring matter occurred in 

 the mesophyll. 



In view of these facts Overton considered that anthocyanin 

 had some connexion with tannins, and was probably a glucoside 

 (p. 247). A similar view was held by Combes,* who called 

 attention to the facts that, as compared with the green leaves, 

 the red autumnal leaves of Ampelopsis hederacea, etc., contain 

 more sugars and glucosides, the amount' of anthocyanin yary- 

 ing directly as the sugars and glucosides ; that the dextrins 

 diminish as the sugars and glucosides increase ; and that the 

 formation of anthocyanin is not apparently dependent on the 

 insoluble carbohydrates. For these and other reasons he con- 

 cluded that the substance in question was probably a cyclic 

 glucoside which arose, not at the expense of pre-existent 

 sugars and glucosides nor of chromogens, but in the ordinary 

 course of constructive metabolism ; also, he concluded, it was 

 only formed provided that oxygen be present. 



The observations of Boodle f also indicate the relationship 

 between anthocyanin and sugar. He found that in the leaves 

 of Rheum, some of the veins of which had been accidentally 

 severed, anthocyanin made its appearance in the mesophyll sup- 

 plied by these veins. Boodle then experimented with species 

 of Oenothera ; all the species examined were not equally 

 responsive, but in the case of O. biennis the severance of the 

 midrib at about its middle caused the whole region distal to 

 the cut to become red provided the plant were exposed to 

 daylight. The operation interrupted the path of transport of 

 carbohydrate from the leaf, so that sugar accumulated above 

 the cut, and it is this concentration of soluble carbohydrates 

 which leads to the. development of anthocyanin. In this con- 

 nexion the work of Linsbauer J may be referred to. 



* Combes : " Ann. Sci. Nat. Bot.," 1909, 9, 274. 

 f Boodle : " New Phytologist," 1903, 2, 207. 

 Linsbauer : " Oestr. Bot. Zeit.," 1901, 51, i. 



