90 



the inter-relation of these enzymes is disturbed, with the result 

 that the respiratory chromogens become evident by their color. 

 The fact that these respiratory chromogens may take up oxygen 

 and later give it up again under the influence of reducing sub- 

 stances, led Palladin to call the respiratory chromogens the 

 " phyto-haematins " because he thought they were similar to the 

 oxygen-carrying pigments of the blood of animals. 



This work of Palladin and his students upon respiratory 

 chromogens is a valuable contribution to our knowledge of the 

 respiration of plants. His conception of the respiratory pig- 

 ments as being cyclic compounds bound to the sugars in the 

 form of glucosides which are insoluble, seems to be founded on 

 fact. In the case of indigo-blue, according to Walther^^ and also 

 in the case of many other pigments, the chromogen is held in 

 the insoluble glucoside form, from which it is separated by the 

 hydrolytic enzymes to give sugars, and then the oxidases attack 

 the chromogen thus set free, imparting to it a definite color. 

 In Schenckia hlumenaviana, Molisch^'^ found that the green plant 

 became red upon treatment with chloroform vapor. This result 

 he attributed to the action of an enzyme upon a chromogen in the 

 plant. In certain of the Dipsacaceae, Miss Tammes^^ demon- 

 strated the presence of a colorless chromogen dipsacan which, 

 under the influence of oxidases, was changed to a blue pigment 

 called dipsacotin by this investigator. Miss Wheldale^^ believes 

 that the red colorations of certain leaves and flowers are caused 

 by anthocyan, a pigment resulting from the coordinated action 

 of oxidases and hydrolytic enzymes. She also considers that 

 the color or lack of color in the offspring of such plants is due 

 to the action of oxidases and reducing substances, etc., as factors 

 in heredity. Overton^" and also Tswett^^ came to the con- 



"Walther. Zur Frage der Indigo-bildung. Ber. Bot. Gesell. 27: loi. 1909. 

 ^' Molisch. Ueber ein neues, einen karminroten Farbstoffe erzeugendes Chro- 

 mogen bei Schenckia hlumenaviana. Ber. Bot. Gesell. 19: 149. 1901. 



48 Miss Tammes. Dipsacan und Dipsacotin, ein neues chromogen und neues 

 Farbstoffe der Dipsaceae. Recueil. Trav. Bot. Neerland. 5: 51. 1908. 



49 Miss Wheldale. Plant Oxydases and Chemical Relationships of Color Va- 

 rieties. Prog. Rei. Botan. 3: 457. 1910. 



«° Overton. Beobachtungen und Versuche iiber das Auf treten von rothem Zell- 

 saft bei Pflanzen. Jahrb. Wiss. Botan. 33: 171. 1899. 



"Tswett. Ueber den Pigmente der Herbstlich-vergilbten Laubes. Ber. Bot. 

 Gesell. 26a: 98. 1908. 



