72 Various Tints of Autumnal Foliage. [January, 



therefore disposed to attribute the -formation of the red 

 colouring matter to some change which takes place when 

 the leaves are not actually dead, but in a state of very low 

 vitality. Of course this is scarcely applicable to those in 

 which a red colour is a normal constituent ; but, at the same 

 time, even then it may indicate more or less of the same 

 kind of condition ; for I have remarked that in those branches 

 of the bilberry which are of a fine scarlet in the early part 

 of the year, the form of the leaves departs considerably from 

 the usual type, as if they were not altogether in a healthy 

 state. Perhaps the fading of green leaves to yellow, and 

 the normally yellow state of some leaves may be referred to 

 a somewhat similar low vitality, which either permits the 

 chlorophyll to become changed or prevents its formation, as 

 in the case of plants growing in the dark. I may here say 

 that there seems every reason to conclude that on further 

 change the red colour so completely fades away as to produce 

 little or no effect on the general tint, since faded red leaves 

 cannot be distinguished from those of the same kind which 

 were not red, and the artificial oxidisation with nitrite of 

 potash, of the substances soluble in water, extracted from 

 scarlet leaves of the bilberry, gives rise to exactly the same 

 colour as in the case of the yellow or green leaves. I may 

 also here say that when scarlet leaves are digested in hot 

 water the red colour is easily removed, and the green, 

 yellow, or brown colours left as the case may be. 



In studying the further changes which occur in leaves in 

 autumn, it is most important to understand the properties 

 of the various colours allied to the chrysophyll group, since 

 it is to them that we must attribute a great part of the more 

 prevailing tints. On the whole, clean scarlets are uncommon 

 in this country in the case of large trees, and simple bright 

 yellows are not very abundant, or only last for a short time ; 

 since the chlorophyll seldom disappears entirely before the 

 chrysophyll is more or less changed. Much remains to be 

 learned with respect to the various kinds of chrysophyll, 

 and the connection between each and the species or special 

 variety of the plant, and the circumstances in which it is 

 placed. As far as my present knowledge enables me to 

 judge, there is some decided connection between the kind of 

 colour and the species of tree, but, at the same time, I have 

 met with entirely different colours in the same species 

 growing in other situations, and I am even disposed to think 

 that there may be individual- differences, analogous to what 

 is so common in the colour of the hair of animals. It is this 

 complication of facts which makes it very difficult to explain 



