680 General Notices. 



addition of water, Anthoxanthin (yellow f!ower) is formed from Chlorophi/ll. 

 8, Anthoxanthin is the colouring matter of yellow flowers. 9. Besides these 

 two colouring matters, we find in white, blue, red, and violet flowers a flower- 

 resin, which may be regarded as the transition between Chlorophyll and An- 

 thokyan. 10. There is also a slightly coloured extractive matter in white and 

 yellow flowers, which is to be considered as the colourless sap of the cells. 

 It is remarkable for its extreme sensibility in regard to alkalies, which colour 

 it yellow. 11. The form of the cells has no influence on the production of 

 a certain colour. 12. Orange-yellow flowers contain both colouring matters, 

 Anthoxanthin and Anthokydn, which is reddened by acids. 13. Brown flowers 

 contain Chlorophyll and Anthokyan, that is reddened by acids. 14. Flowere 

 which contain both colouring matters produce Anthokyan in the epidermis 

 and the upperjayers of the cells, but Anthoxanthin in the interior of the cells. 

 15. Anthokyan is also the colouring matter of the other red leaf-like organs; 

 but is, in such cases, covered by a colourless epidermis. 16. A black colouring 

 matter does not exist in leaf-like organs ; plants concentrate so much blue, 

 violet, or green tint, that it seems to us a black. 17. The alteration of the 

 colour of flowers must be observed with reference to the different periods 

 of the life of the plants. 18. Yellow proceeds directly from green. 19. After 

 the period of fructification, yellow passes frequently to the opposite range of 

 colours. 20. All buds of red and blue flowers pass from green through 

 white to red. 21. White is the transition-step to blue. 22. Blue flowers 

 are red in bu J, because they have not begun to respire. 23. Some blue flowers 

 become red, and others white, after the period of flowering. 24. The blue 

 colour subsequently acquired by many red flowers may be explained in two 

 modes. (^Edinburgh New Philosophical Journal, p. 430. April, 1836.) 



On the selecting Poiver of the Roots of Plants. — A great many experiments, 

 which appear to have been conducted with an extraordinary degree of nicety 

 and accuracy, have been made, in order to determine the extent of this power, 

 by Dr. Daubeny, the Professor of Botany and Chemistry in the University of 

 Oxford. 



The subject was taken up by Dr. Daubeny, in consequence of its being 

 recommended for consideration by the British Association for the Advance- 

 ment of Science, during their meeting at York in 1831 ; and also because 

 this eminent chemist had been previously engaged in enquiries of the same 

 nature. The result serves to confirm the conclusions deduced by the younger 

 Saussurefrom his experiments on vegetation; viz. that plants have a power of 

 selecting the liquids absorbed by their spongioles, with, however, a certain 

 modification to be noticed. 



" In the experiments that were made by Braconnot, Schrader, and others, 

 with a similar intent to my own, the plants operated upon, in order that all 

 external sources for the supply of earthy matter might be cut off", were made 

 to vegetate either in washed sand, in sulphur, in pounded glass, in small shot, 

 or in certain metallic oxides. It occurred to me, however, that, without 

 placing thern under circumstances so unnatural, and consequently so un- 

 favourable to growth, the same end would be fulfilled if the seeds were sown 

 in some earth, which, though foreign to their constitution, agreed, neverthe- 

 less, more nearly in mechanical properties with those contained in the soil 

 in which they were wont to grow. It was with this intent that I was 

 originally led to select, as a soil for my plants, the sulphate of strontian 

 (which is obtained in abundance near Bristol) reduced to fine powder ; and 

 having found that the ashes of plants which had been reared in this matrix 

 seemed to contain no ti'ace of the earth, I was led, in the next place, to try 

 whether this might be owing merely to the insolubility of the substance in 

 question ; for which reason I varied the experiment, by watering my plants 

 with a weak solution of nitrate of strontian. It will appear, from the subse- 

 quent detai's, that, in either form of the experiment, lime, and not strontites, 

 was the earth that presented itself; but as, in proportion to the care that had 

 been taken to exclude any external source of supply of earthy matter, the 



