1871J Various Tints' of Autumnal Foliage. 67 



their more or less red colour, which is made more intense by 

 acids, and more purple, blue, or green by alkalies. This is 

 because there is strong absorption in the green part of the 

 spectrum, and the broad bandj is raised towards the blue 

 end by acids, and lowered towards the red by alkalies, which 

 also often increase the absorption at the blue end, so as to 

 make the colour green, though I am much inclined to 

 believe that in most cases this is due to the presence of a 

 second yellow-coloured substance, so that a mere difference 

 in colour is no proof that the red colours differ. Usually, 

 but not invariably, they are soluble in water and aqueous 

 alcohol, but not in bisulphide of carbon. Very many species 

 are met with in fruits, flowers, and roots, distinguished by 

 their spectra, either in their natural state or when acted 

 upon by various reagents, and so far I have found at least 

 six in leaves. That which gives rise to the red patches in 

 the beautiful, variegated leaves of some of the geraniums of 

 our gardens, is the same as that met with in the flowers of 

 particular species. The purple colour of the leaves of 

 turnips is the same as that of the purple flowers of the 

 common garden stock. The colour of red cabbage has well- 

 marked peculiarities, and so has that of the root and leaves 

 of the beet. The dark leaves of Tamus communis contain 

 another distinct colour, and so do those of the purple beech, 

 but all these are normal constituents of the young leaves of 

 particular varieties of the plants, and not simply developed 

 towards autumn. It is, however, impossible to draw a line 

 between the two cases, since the colour which gives rise to 

 the dark brown tint of heath in autumn appears to be the 

 same as that of the purple beech, and that which occurs in 

 the dark leaves of ivy seems to correspond with the fine 

 deep pink colour developed in many leaves only in autumn, 

 so as to give rise to the splendid red and scarlet, which pro- 

 duce such a fine effect on certain kinds of scenery. 



In order to obtain these red colouring matters in a satis- 

 factory state for experiment, the leaves should be boiled in 

 alcohol, which dissolves chlorophyll, xanthophyll, and the 

 reds ; but, as I have already described in previous 

 papers, the alcoholic solution of most of them rapidly fades, 

 so that the solution is only of a dirty green or yellow tint. 

 On evaporating it to dryness, the splendid red colour chiefly 

 collects round the edges, and the chlorophyll and 

 xanthophyll are deposited more in the centre, so that we 

 can immediately see that there is a mixture. By re- 

 dissolving in water, the chlorophyll and xanthophyll are left 

 insoluble, and theerythrophyll is obtained in solution, and on 



