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ALTERATIONS OF COLOUR. 
CHAPTER III. 
ALTERATIONS OF COLOUR. ! 
CHANGES in the colour of the several organs of plants 
are more often either pathological or the result of 
variation than of malformation properly so called. 
Alterations in colour arise from a diminished or an 
increased amount of colouring matter, or from an un- 
usual distribution of the solid or fluid matters on which 
the colour depends. The superposition of cells con- 
taining colouring material of different tints produces 
naturally a very different set of hues from those which 
are manifested when the colours are not blended. 
Referring the reader to the ordinary text-books on 
vegetable physiology and chemistry for details as to 
the nature and disposition of colouring materials in 
plants under natural circumstances, it will only be 
necessary to cite a few instances of deviation from the 
general colour of plants or their organs. 
Albinism— This change is due to the deficient forma- 
tion of green colouring matter or chlorophyll, and is 
more a pathological condition than a deformity. 
It seems necessary to draw a distinction between 
this state and ordinary blanching or etiolation. In 
the former case chlorophyll seems never to be formed 
in the affected parts, even if they be exposed to light, 
while an etiolated organ, when placed under favorable 
circumstances, speedily assumes a green colour. In 
Richardia cethiopica one or more leaves become occa- 
sionally as white as the spathe is usually. 
1 These deviations are treated of under the head of alterations of 
form, because they are not, in a teratological point of view, of sufficient 
importance to demand a specific heading, while they appeal to the 
sight in the same way as the deviations from the customary forms of 
organs. 
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