202 ANTHOCYANINS AND GENETICS 



Thonerde und Eiseuvitriol die rothe Farbe der Hortensienbliithe in 

 die blaue umzuwandeln vermoge." He points out that the pigment 

 of the flowers is anthocyanin, and in sections of the petals the colour is 

 similarly turned blue on addition of solutions of iron and aluminium 

 salts. He further emphasises the fact that all plant anthocyanins do 

 not behave in the same way, and hence this may be one of the reasons 

 why it has not been possible to change the flower-colour of other plants 

 by adding salts to the soil. 



In 1906, Kraemer (503) gives an account of a number of experi- 

 ments which he made to test whether flower-colours can be modified by 

 treating the soil with chemical substances. The compounds he used 

 were : acetic acid, citric acid, malic acid, phosphoric and other acids ; 

 various iron salts, such as acetate, citrate, chloride and sulphate; 

 certain aluminium salts, such as sulphate, phosphate, and the double 

 salts of aluminium and potassium sulphate, and aluminium and am- 

 monium sulphate; ammonia water, potassium hydrate, ammonium 

 nitrate, potassium nitrate, potassium iodide, iodine and potassium 

 cyanide. These were supplied in solution through the soil, beginning 

 with 1 : 10,000 of water, and the strength gradually increased until 

 1 : 1000 of water was reached. Most of the substances could be supplied 

 in this strength every five days for some months without injury to the 

 plants. There were no marked effects. In yellow roses supplied with 

 aluminium and potassium sulphate, the leaves and stems became 

 slightly reddish. ' La France ' roses treated with iron citrate and citric 

 acid had uniformly pink petals. Some rather insignificant changes 

 were noted in other plants. The scarlet carnation showed a tendency 

 to form white streaks with iron and ammonium sulphate, aluminium 

 phosphate, iron citrate and citric acid ; also a maroon carnation treated 

 with ferrous sulphate. The petals of a white carnation when fed with 

 potassium and aluminium sulphate showed a tendency to form red 

 streaks. 



Later, in 1908, Vouk (522) repeated a number of experiments on 

 the same lines as Molisch, using plants of Hortensia (Hydrangea hortensis). 

 Vouk remarks, as a preliminary, that Miyoshi (? 187) has succeeded in 

 changing the lilac colour of Callistephus chinensis and Campanula 

 alliariaefolia into blue, and the red of Lycoris radiata into .lilac by 

 artificial treatment. Of Molisch's experiments he observes that the 

 leaves of the plants used were frequently injured, and this may be due 

 to too large quantities of salts added. He therefore set out to deter- 

 mine (1) how the change to blue colour is affected by different quantities 



