1871.] Various Tints of Autumnal Foliage. 75 



leaves is moderately strong alcohol, to which a few drops of 

 hydrochloric acid have been added. Since they are almost 

 insoluble in hot neutral alcohol, it is well to digest the 

 leaves first in it, to remove some of the xanthophyll, and 

 any other colour soluble in the liquid. After evaporating to 

 dryness the solution in hot acid alcohol, any colour soluble 

 in water should be dissolved out, and the insoluble portion 

 digested in a cold mixture of alcohol and water, in equal 

 parts, with a little hydrochloric acid, which dissolves much 

 of the phaiophyll, and leaves an impure xanthophyll. After 

 evaporating the clear solution to dryness, strong neutral 

 spirit dissolves the more pure colour, which is always darker 

 and browner when dry than when in solution. As thus 

 obtained, it may be, and often is, a mixture of various 

 coloured substances, and it is only by comparing those from 

 different specimens of leaves that we can arrive at a satis- 

 factory conclusion respecting them. For example, beech 

 trees are occasionally found whose leaves turn in autumn 

 to a very deep colour, almost exactly like burnt sienna. 

 These yield a fine red phaiophyll colour, which, when dry, 

 is redder than burnt sienna, and almost exactly like so-called 

 " light-red." When dissolved in alcohol it is of a fine pink- 

 red colour, and corresponds in every particular with that 

 obtained by oxidising the chrysophyll of yellow beech leaves 

 as described above. The leaves of other beech trees turn to 

 an orange-colour, like burnt sienna mixed with raw sienna, 

 and these yield what appears to be a mixture of the above 

 red colour with the browner modification into which the red 

 passes, as already explained ; and those leaves which have 

 remained some time on damp ground contain still less of the 

 red and more of the brown, which, when approximately pure, 

 has a tint like that of a mixture of burnt sienna with burnt 

 umber. Besides these, neutral alcohol or water extracts 

 from the leaves a colour which closely corresponds with the 

 orange modification already mentioned ; and thus it will be 

 seen that the actual tint of the leaves is the result of a 

 mixture sometimes of at least six different colouring matters. 

 I have not been able to obtain from the leaves of the elm, 

 chesnut, poplar, or oak, any pink-red colour corresponding 

 to that first formed when the chrysophyll is artificially 

 oxidised, but only the brown modification of burnt umber 

 tint which corresponds almost exactly with what is formed 

 on keeping the artificially oxidised in a dry state. This 

 absence of the redder colour appears to be because it passes 

 into the brown modification much more rapidly than the 

 analogous colour in beech leaves, so that whilst they remain 



