1871.] Various Tints of Autumnal Foliage. j$ 



the cause of some of the results, but, at the same time, this 

 variation is in complete agreement with the varied tints of 

 different trees of some species. 



One of the most striking kinds of chrysophyll which has 

 much influence on autumnal tints is that contained in yellow 

 beech leaves. It is of pale yellow colour, but when dissolved 

 in alcohol and oxidised by means of nitrate of potash and 

 hydrochloric acid, it is changed to deep pink-red. When 

 dissolved in water the oxidisation gives rise to a very copious 

 precipitate of the same colour, which is, therefore, apparently 

 only imperfectly soluble in water, but more easily in acid 

 alcohol. This kind of chrysophyll appears not to be formed 

 till the time when the leaves begin to turn yellow, since 

 I found that green beech leaves contained much of another, 

 which is often associated with the one just described in other 

 trees. The yellow leaves contain the yellow xanthophyll, 

 whereas the orange-brown leaves contain the orange modifi- 

 cation, as though, perhaps, derived from the other by partial 

 oxidisation. I have met with this kind of chrysophyll in the 

 leaves of the bilberry, and in some varieties of plane, and 

 in a less pure state in many others. Another species of 

 chrysophyll found in many leaves may be procured from 

 some varieties of the common elm. I have found that leaves 

 of large size and loose texture give it in the most pure state, 

 but in some it is mixed with much of the kind found in the 

 beech, and in others is almost entirely replaced by a third 

 colour, which is but little altered by nitrite of potash. The 

 colour to which I wish, however, to call especial attention 

 turns to a pink-orange when thus oxidised, and gives a 

 spectrum with a sufficiently well-marked narrow absorption- 

 band, in the centre of the green, and a fainter nearer to the 

 blue ; but after a while these bands fade, and the colour 

 becomes orange-yellow. I have met with this colour in the 

 leaves of the poplar, Spanish chesnut, alder, apple, and 

 oak ; and, as far as I am able to judge, there are very 

 many trees whose leaves contain variable mixtures of this 

 with that found in yellow beech. 



I have met with a very special kind of chrysophyll in the 

 leaves of a plane tree, which turns to a very fine yellow. 

 This gives, on oxidisation by nitrite of potash, a pink colour, 

 with a very well-marked absorption-band in the green, 

 nearer to the red end than in the case of that met with in 

 the elm. In the green leaves of other planes of the same 

 species I found only that colour so common in yellow beech 

 leaves, and I have noticed that such plane leaves do not 

 turn yellow, but to an orange-brown, modified by the 



VOL. VIII. (O.S.) — VOL. I. (N.S.) L 



