In some cases the plastid disappears and the crystalline pigment only is left.
The composition of the pigment is quite similar to that of lapis lazuli; but the constitution of both is uncertain.
Starch grains may often be seen in contact with the pigment crystals.
The absorption of these rays implies that the pigment absorbs radiant energy from the sun, and gives us some explanation of its power of constructing the carbohydrates which has been mentioned as the special work of the apparatus.
It is chiefly used as a pigment and in the manufacture of flint glass.