420 



erytlirogen, and the alkalis on xanthogen. 2dly, That the com- 

 pound of alkalis and xanthogen is of a yellovr colour, and that when 

 a blue infusion is changed to green, it is owing to the gradual inter- 

 mixture of the newly generated yellow with the original blue. 



Camellia Japonica. — The blossoms of the beautiful double white 

 Camellia Japonica are remarkable for the peculiar matters which they 

 contain, two of which appear to be distinct vegetable principles. 

 When a parcel of the petals is infused in boiling-hot water, and 

 digested for some time, a nearly colourless infusion is obtained, which 

 is not visibly affected by acids. When solution of potash is added, a 

 light orange colour appears, which gradually deepens, till in a few- 

 hours it acquires a very deep orange hue. Solution of ammonia 

 causes a similar effect. When lime-water is employed, it produces 

 turbidity in the infusion, and a pinkish red colour. This colour 

 gradually assumes a richer tint, and in about 24 hours exhibits a 

 deep pinkish red. The author has applied the same alkalescent 

 agents to above 150 flowers, both white and coloured, without ob- 

 serving any similar effect. 



To this colourable matter he gives the name of Camelline. The 

 author tried the effects of various reagents, but no interesting facts 

 resulted. 



When any portion of the flower-leaf is bruised, whether remain- 

 ing on the parent plant or removed from it, it immediately begins to 

 assume a rusty or ochry tint, which grows deeper and deeper, till it 

 arrives at the tint of perfect ochre. 



By various experiments, it was pi-oved that this change of colour 

 depends upon the action of the oxygen of the air. It takes place in 

 a very remarkable degree in oxygen gas, and does not take place at 

 all when the contact of air is excluded by an immersion in mercury, 

 in hydrogen, or carbonic acid gas. To this brown-growing matter, 

 viewing it as a distinct vegetable principle, Dr Hope gave the name 

 of Magnoline, in consequence of its occurring in a very remarkable 

 degree in the Magnolia grandiflora and Magnolia conspicua. A third 

 remarkable circumstance respecting the Camellia petals, is, that they 

 contain a notable quantity of iron. This was little to be expected, 

 seeing that iron is so common a source of colour, and the blossom is 

 entirely colourless. The author was led to search for this metal in 

 consequence of the strong resemblance which the colour which prot- 

 oxide and protocarbonate of iron acquire by the absorption of oxy- 

 gen from the air, and the colour acquired by the bruised petals of 

 the Camellia bear to each other. Dr Hope is satisfied that the ochry 



