It consists essentially of a number of minute corpuscles or plastids, the protoplasmic substance of which is impregnated with a green coloring matter.
These plastids are especially charged with the duty of manufacturing carbohydrates from the carbon dioxide which the air contains, and which is absorbed from it after it has entered the intercellular passages and has so reached the cells containing the plastids.
Chromatophores.The chromatophores or plastids are protoplasmic structures, denser than the cytoplasm, and easily distinguishable from it by their color or greater refractive power.
The coloring matters are not dissolved in the stroma of the chrornoplast, but exist as amorphous granules, with or without the presence of a protein crystal, or in the form of fine crystalline needles, frequently curved and sometimes present in large numbers, which are grouped together in various ways in bundles and give the plastids their fusiform or triangular crystalline shape.
In addition to the plastids, there are found in some plant-cells, e.g.
Cream-coloured flowers are regarded as white because cream is due to yellow plastids and not to sap colour.
As a rule they are highly coloured, the colouring matter being contained in the cell-sap, as in blue or red flowers, or in plastids (chromoplasts), as generally in yellow flowers, or in both forms, as in many orange-coloured or reddish flowers.