AI-TERATIONS OF fOTX^m. '.]{\J 



CHAPTER III. 



ALTERATIONS OF COLOUR.^ 



Changes in the coloiu' 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 part^ even if they be exposed to light, 

 while an etiolated organ, when placed under favorable 

 circumstances, speedily assumes a green colour. In 

 Ricliard'm a'thioplca one or more leaves become occa- 

 sionally as white as the spathe is usually. 



* These deviations are treated of under the head of alterations of 

 form, because they are not, in a teratological point of vievr, 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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