98 



The cause of this changeability is somewhat uncer- 

 tain. It is upon the oxygen, combined with their 

 parenchyma, that the colour of a petal depends ; for 

 sulphurous acid (the fume arising from a burning 

 match), w T hich has a most powerful affinity for oxy- 

 gen, destroys the hue of all coloured flowers, though 

 it leaves that of white flowers unchanged. Mr. Smith- 

 son's experiments, and those of M. Schubler, seem 

 to indicate that the colouring matter of flowers and 

 fruits is fundamentally blue — rendered red by acids 

 or the addition of oxygen, or yellow by the presence 

 of an alkali or the subtraction of oxygen. Mr. Smith- 

 son says that the colouring matter of the violet is the 

 same in the ruddy tips of the daisy, geranium, blue 

 hyacinth, hollyhock, lavender, and various plums, in 

 the leaves of the red cabbage, and in the rind of the 

 salmon raddish. The acid which causes the red tint 

 seems to be usually the carbonic. 



Remarking upon the mutability of colour in some 

 dahlias, a very sensible writer has observed, that such 

 has been the improvement in this flower that it would 

 be almost impossible to recognize Antagonist, Cleopa- 

 tra, Essex Bride, Marchioness of Ormonde, Lady 

 Antrobus, Admiral Stopford, Beauty of England, or 

 Oakley's Surprise, as descendants from the star- 

 shaped Dahlia variabilis , introduced about the year 

 1800 ; but although the single purple and yellow 

 dahlias of that day have been changed into colours 



