1898J COLOURING MATTERS OF FLOWERS 195 



experimented on flower colours with alkalies and acids as his only 

 reagents. By the employment of neutral reagents, however, such as. 

 acetates of lead and magnesium, the results are such as to afford 

 ground for distinction between the various hues and tints. For 

 instance, the fine green precipitate yielded by acetate of lead with the 

 colouring matter of the rose tribe is turned red again by acetic 

 acid, but the similar precipitate given by the blue pigment of 

 harebell corolla is turned blue by this acid ; and with acetate 

 of magnesium and acid the effects are similar. The blue of 

 scabious when treated with acetate of lead yields a similar green 

 colour and precipitate, but on adding acetic acid we have a red 

 liquid and a still green precipitate, the portion lying under the acid 

 liquid gradually turns blue, while the portion outside the liquid,, 

 though still bathed therewith, remains green. This interesting 

 experiment seems to clearly suggest a radical difference in the 

 composition or constitution of the normal red and blue pigments 

 of flowers, but likewise proves the fallacy of the early view that 

 ' rose, blue, and violet flowers owe their tints to one and the same 

 substance influenced by the reactions of the vegetable juices.' 

 Similar experiments even seem to show that certain distinctively red 

 flowers, such as camellia, owe their tint to a substance which is not 

 the same as that of other red flowers, such as rose ; but in this case 

 there is more than a suspicion that the real and original colour of 

 the former kind is blue and not red, and that artificial means could 

 practically effect the change. Even acetate of lead when used alone 

 to react on various red colouring matters of vegetable origin produces 

 results which argue an essential diversity therein. Thus, with 

 genuine red wine it yields a greyish-blue or greenish colour, with 

 the colouring matter of bilberries it gives a blue precipitate, with 

 that of mallow or elderberries a green, and with that of phytolacca 

 berries a red-violet precipitate. V. Vogel, experimenting later, 

 found that by using a concentrated solution of sulphate of copper 

 the colour of new or old red wines was decolourised, although the 

 fresh pellicle of the grape itself is coloured violet by this reagent, 

 as is also the extract of cherry juice ; while that of bilberry 

 remained unchanged. By the action of sub-acetate of lead bilberry 

 juice is completely decolourised, while that of cherry is not 

 decolourised in the presence of alcohol or of red wine. The 

 spectroscope has also been employed to distinguish between these 

 diverse pigments, but its revelations need not be referred to here,, 

 especially as I am disposed to consider them to be not so very 

 valuable owing to the extreme difficulty of isolating completely the 

 different colouring matters. 



A decided advance was made towards a veritable chemical com- 

 prehension of the subject when Morren declared that the red and blue 



