74 Various Tints of Autumnal Folioge. [January, 



continued presence of chlorophyll, though, when this has been 

 dissolved away by means of alcohol, the former colour can 

 be very clearly seen. 



It is very probable that other kinds of chrysophyll will be 

 found on more extended examination, and that a more 

 complete knowledge of their properties will serve to explain 

 many facts which are still obscure. I have, indeed, even now 

 good reason for believing in the existence of some others, 

 but their characters do not differ sufficiently from those 

 described to materially modify the general results. 



The alcoholic solutions of all these various kinds of 

 chrysophyll resemble one another in being changed by 

 oxidisation with nitrate of potash and hydrochloric acid to 

 pink-red substances, which alter more or less slowly into 

 orange colours. When thus changed, and kept dry, or in 

 solution with a slight excess of ammonia, they are further 

 modified into various brown substances. This is well seen 

 in the case of the red colour obtained from beech leaves, 

 which, on the addition of ammonia, shows a well-marked 

 absorption-band in the orange. This slowly disappears, 

 and, after keeping for awhile, when evaporated to dryness, 

 it is nearly as brown as burnt umber, and the addition of 

 hydrochloric acid to the solution does not restore it to the 

 original fine pink-red, but we have a decided brown colour, 

 to some extent absorbing the red end of the spectrum, which 

 was previously quite clear. All these modified colours, when 

 dissolved in sulphuric acid diluted with an equal bulk of 

 water, and still further oxidised by means of chlorate of 

 potash, merely fade, and are thus in that state of oxidisation 

 which is characterised by a maximum depth of colour. 

 These different changes may be simply due to an alteration 

 of the chrysophyll, but, at the same time, there are cases 

 which seem to indicate that almost, or quite, colourless 

 compounds may contribute to the production of deep colours. 

 For example, when the fresh leaves of Acuba japonica are 

 digested in cold alcohol, the solution evaporated to dryness 

 and treated with water, a clear yellow solution is obtained, 

 which, when evaporated at a gentle heat, turns dark brown, 

 on account of the formation of an insoluble substance of that 

 tint. Water then extracts the apparently unaltered yellow 

 substance ; and, though these facts are an exception to the 

 general rule, they seem to show that a dark colour may be 

 formed independent of the previous existence of a colouring 

 matter of the chrysophyll group. 



Though some of the various phaiophyll colours are 

 soluble in water, the proper solvent to extract them from the 



