116 REACTIONS INVOLVED IN [CH. 



involved are the hydrolysis of a glucoside and subsequent oxidation. 

 Quite similar pigments have been described by Parkin, Bartlett, Tammes 

 and others 1 . The reactions taking place in the formation of the 

 respiration pigments of Palladin are probably of the same nature. 

 An analogous case too is the development of blue pigment in the white 

 flowers of an Orchid (Phajus sp.) on the death of the tissues. The change 

 of colour has been used to determine the death-point of the protoplasm 

 when subjected to freezing 2 . 



3. Evidence from the connection of anthocyanin formation ivith 

 photosynthesis. It has already been stated in Chapter vi, that a very 

 definite connection exists between photosynthesis and the appearance 

 of anthocyanin. In organs, such as green leaves, in which photo- 

 synthesis takes place to the greatest extent, there is least production 

 of anthocyanin. In organs, on the other hand, such as flowers, which 

 are unable to carry on photosynthesis, there is the greatest formation 

 of pigment. All intermediate conditions may be found between these 

 two extremes and the same relationship will be found to hold. From 

 these data, the deduction can be made that the greatest concentration 

 of sugar arises in tissues where photosynthesis is most active. Thus, 

 in leaves, there is abundant sugar to combine with the chromogen, 

 and provided translocation of all synthetic products away from the 

 leaf is unhindered, the direction of the reaction suggested in the hypo- 

 thesis will be : 



chromogen + sugar - glucoside + water 



Under these conditions there would be no tendency for free chromogen 

 to exist, and consequently no anthocyanin would be formed. 



4. Evidence from the results of the blocking of the translocation 

 current. It has also been stated that injury to the tissues, through 



1 Parkin, J., 'On a brilliant Pigment appearing after Injury in species of Jacobinia,' 

 Ann. Bot., Oxford, 1905, xix, pp. 167-168. 



Bartlott, H. H., 'The Purpling Chromogen of a Hawaiian Dioscorea,' U.S. Dept. of 

 Agriculture, Bureau of Plant Industry, Bull. 264, 1913. 



Tammes, T., 'Dipsacan und Dipsacotin, cin neues Chromogen und ein neuer Farbstoff 

 der Dipsaceae,' Bee. Trav. Bot. Neerl., Nijmegen, 1908, v, pp. 51-90. 



Palladin, W., 'Die Bildung roten Pigments an Wundstellen bei Amaryllis vittata,' 

 Ber. D. hot. Ges., Berlin, 1911, xxix, pp. 132-137. 



2 Miiller-Thurgau, H., 'Ueber das Gefrieren und Erfrieren der Pflanzen,' Landw. Jahrb., 

 Berlin, 1880, ix, pp. 133-189. Also: 



Prillieux, Ed., 'Coloration en bleu des fleurs de quelques orchidees sous 1'influence de 

 la gelee,' Bui. soc. hot., Paris, 1872, xix, pp. 152-157. 



Bommer, J. E., ']tude sur le bleuissement des fleurs du Phajus maculatus Lindl.,' 

 Butt. soc. hot., Paris, 1873, xx, pp. xxvii-xxxiii. 



