194 Proceedings of the Royal Society of Edinburgh. 



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 

 tints of thp Camellia are in no way dependent on, or connected with, 

 the iron which it contains. 



Magnolia Grandiflora. — "When the petals of the Magnolia 

 Grandiflora are boiled for some time in distilled water, a liquor of 

 a very light yellowish brown is obtained. This colour is banished 

 by sulphuric acid. Solution of potassa immediately causes a deep 

 gall-stone yellow, shewing that this, like other white flowers, con- 

 tains no erythrogen, but abounds in xanthogen. That matter, which 

 becomes of an ochry hue by the contact of air, is very abundant in 

 the Magnolia, so that, if the cuticle be scraped off, in less than a 

 minute the place of abrasion exhibits the ochry tint. The petals of 

 the snow-white Magnolia conspicua exhibit the same phenomena in 

 a still more remarkable degree. If a petal of this beautiful flower 

 be bruised between the finger and thumb, it immediately becomes 

 of a very deep brown, and ere long almost black. Some other white 

 flowers, by being crushed and exposed to the air, also acquire the 

 ochry tint, but in a much inferior degree to those already men- 

 tioned. The ochry-growing matter is not confined to white flowers. 

 It exists in different species of the blue flowers of the Aconitum, 

 particularly the napellus. 



The third flower of which Dr Hope gave an account, was the 

 Chrysanthemum leucanthemum, the ox-eye daisy. A strong decoc- 

 tion of the white petals exhibits a light brown colour, which potash 

 quickly converts into the usual gall-stone yellow. When sulphuric 

 acid is dropped into this decoction, the colour becomes a light prim- 

 rose yellow, and the liquid immediately assumes a gelatinous state. 

 This jelly gradually becomes more consistent, and, in about a quar- 



