As examination of the petals of the red rose “George Dickson,” has shown that the anthocyen pigment contained therein is the cyanidin glucoside, cyanin. It is present to the extent of about 9—10 per cent. by weight of the dried petals, and exists in the petals as an oxonium salt (
i. e
., in combination with a plant acid). A yellow glucoside sap-pigment also occurs in the same flowers, but beyond the fact that it has been shown to be capable of producing an anthocyan, by reduction, and that it is not a glucoside of the flavonol myricetin, it has not been further identified, on account of the small quantity present. Further work may show it to be a glucoside of quercetin, and corroborate the work of Dr. Everest, on the purple-black viola, in which it was shown that an anthocyan (“violanin”) and the flavonol glucoside from which it could be produced, by reduction (a glucoside of myricetin), are present, side by side, in the same flowers. This would be additional evidence in favour of the hypothesis that “anthocyans are produced, in nature, by the reduction of the flavonols.” It is interesting to note that this rose, grown in Australia, contains the same colouring matter as was isolated by Willstätter and Nolan from the rose known as “Rosa Gallica,” grown in Europe, and shows how widely these colouring matters are distributed in nature. The rose “George Dickson” was chosen for this investigation on account of its deep red colour, which would indicate a fairly large percentage of the anthocyan pigment. The flowers from which the petals were gathered were grown by Mr. G. Knight, at his nursery, Parramatta Road, Homebush, and his generosity in supplying me with sufficient material enabled the work to be successfully accomplished.
Effect of Rose ( Rosa gallica ) Flowers Color on the Infestation by the Rose Aphid, Macrosiphum rosae (Linnaeus)