On the Colour of Leaves of Plants and their Autumnal Changes

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                                but little colour. The green alcoholic solution was before evaporation 
neutral, but subsequently and after the developement of the red 
colour, it was found to possess a slightly acid re-action, owing 
no doubt to the concentration by evaporation of a minute quantity 
of acid present in the alcoholic solution and it was to this acid 
that the appearance of the red colour was due. Had the final 
reaction been neutral or slightly alkaline, a blue, and not a red 
colour would have ensued. The fact may here be recalled to mind, 
that, as in the Gloire de Dijon rose, the mature leaves of the Castor 
oil plant are also of a deep green.
I will now refer briefly to another plant, an evergreen, a 
species of Crataegus, the young leaves of which attracted my attention 
from the peculiarity of their colour, they were a pale blood red 
or orange, the older leaves being of a bright and very pleasing 
green. The alcoholic solution obtained from these <s>cut up <\s> red leaves 
was of a yellow colour with a tinge of green; the pieces of the 
leaves were observed even after the abstraction of the red pigment,
still to exhibit a decided rusty red tint. <s>which was due to iron <\s>
The residue of the evaporated solution was blood red and as 
viewed under the microscope it was found to be composed chiefly 
of red with a little yellow colouring matter, both colours keeping,
as in so many other instances, perfectly distinct; the yellow was 
granular, while the red was translucent, diffused, or in rather large 
and irregular granulations, but there was no line of demarcation 
between the two colours.
On going to look at this evergreen after an interval of about a 
fortnight, I found that the young red leaves had already for the 
most part changed to green and that some of the older leaves 
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Manuscript details

Arthur Hill Hassall
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On the Colour of Leaves of Plants and their Autumnal Changes, 1892. From The Royal Society, AP/69/1



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